This patch adds a new robust_list() syscall. The current syscall can't be expanded to cover the following use case, so a new one is needed. This new syscall allows users to set multiple robust lists per process and to have either 32bit or 64bit pointers in the list.
* Use case
FEX-Emu[1] is an application that runs x86 and x86-64 binaries on an AArch64 Linux host. One of the tasks of FEX-Emu is to translate syscalls from one platform to another. Existing set_robust_list() can't be easily translated because of two limitations:
1) x86 apps can have 32bit pointers robust lists. For a x86-64 kernel this is not a problem, because of the compat entry point. But there's no such compat entry point for AArch64, so the kernel would do the pointer arithmetic wrongly. Is also unviable to userspace to keep track every addition/removal to the robust list and keep a 64bit version of it somewhere else to feed the kernel. Thus, the new interface has an option of telling the kernel if the list is filled with 32bit or 64bit pointers.
2) Apps can set just one robust list (in theory, x86-64 can set two if they also use the compat entry point). That means that when a x86 app asks FEX-Emu to call set_robust_list(), FEX have two options: to overwrite their own robust list pointer and make the app robust, or to ignore the app robust list and keep the emulator robust. The new interface allows for multiple robust lists per application, solving this.
* Interface
This is the proposed interface:
long set_robust_list2(void *head, int index, unsigned int flags)
`head` is the head of the userspace struct robust_list_head, just as old set_robust_list(). It needs to be a void pointer since it can point to a normal robust_list_head or a compat_robust_list_head.
`flags` can be used for defining the list type:
enum robust_list_type { ROBUST_LIST_32BIT, ROBUST_LIST_64BIT, };
`index` is the index in the internal robust_list's linked list (the naming starts to get confusing, I reckon). If `index == -1`, that means that user wants to set a new robust_list, and the kernel will append it in the end of the list, assign a new index and return this index to the user. If `index >= 0`, that means that user wants to re-set `*head` of an already existing list (similarly to what happens when you call set_robust_list() twice with different `*head`).
If `index` is out of range, or it points to a non-existing robust_list, or if the internal list is full, an error is returned.
* Implementation
The implementation re-uses most of the existing robust list interface as possible. The new task_struct member `struct list_head robust_list2` is just a linked list where new lists are appended as the user requests more lists, and by futex_cleanup(), the kernel walks through the internal list feeding exit_robust_list() with the robust_list's.
This implementation supports up to 10 lists (defined at ROBUST_LISTS_PER_TASK), but it was an arbitrary number for this RFC. For the described use case above, 4 should be enough, I'm not sure which should be the limit.
It doesn't support list removal (should it support?). It doesn't have a proper get_robust_list2() yet as well, but I can add it in a next revision. We could also have a generic robust_list() syscall that can be used to set/get and be controlled by flags.
The new interface has a `unsigned int flags` argument, making it extensible for future use cases as well.
It refuses unaligned `head` addresses. It doesn't have a limit for elements in a single list (like ROBUST_LIST_LIMIT), it destroys the list as it is parsed to be safe against circular lists.
* Testing
This patcheset has a selftest patch that expands this one: https://lore.kernel.org/lkml/20250212131123.37431-1-andrealmeid@igalia.com/
Also, FEX-Emu added support for this interface to validate it: https://github.com/FEX-Emu/FEX/pull/3966
Feedback is very welcomed!
Thanks, André
[1] https://github.com/FEX-Emu/FEX
Changelog: - Rebased on top of new futex work (private hash) v4: https://lore.kernel.org/lkml/20250225183531.682556-1-andrealmeid@igalia.com/
- Refuse unaligned head pointers - Ignore ROBUST_LIST_LIMIT for lists created with this interface and make it robust against circular lists - Fix a get_robust_list() syscall bug for getting the list from another thread - Adapt selftest to use the new interface v3: https://lore.kernel.org/lkml/20241217174958.477692-1-andrealmeid@igalia.com/
- Old syscall set_robust_list() adds new head to the internal linked list of robust lists pointers, instead of having a field just for them. Remove tsk->robust_list and use only tsk->robust_list2 v2: https://lore.kernel.org/lkml/20241101162147.284993-1-andrealmeid@igalia.com/
- Added a patch to properly deal with exit_robust_list() in 64bit vs 32bit - Wired-up syscall for all archs - Added more of the cover letter to the commit message v1: https://lore.kernel.org/lkml/20241024145735.162090-1-andrealmeid@igalia.com/
--- André Almeida (7): selftests/futex: Add ASSERT_ macros selftests/futex: Create test for robust list futex: Use explicit sizes for compat_exit_robust_list futex: Create set_robust_list2 futex: Wire up set_robust_list2 syscall futex: Remove the limit of elements for sys_set_robust_list2 lists selftests: futex: Expand robust list test for the new interface
arch/alpha/kernel/syscalls/syscall.tbl | 1 + arch/arm/tools/syscall.tbl | 1 + arch/m68k/kernel/syscalls/syscall.tbl | 1 + arch/microblaze/kernel/syscalls/syscall.tbl | 1 + arch/mips/kernel/syscalls/syscall_n32.tbl | 1 + arch/mips/kernel/syscalls/syscall_n64.tbl | 1 + arch/mips/kernel/syscalls/syscall_o32.tbl | 1 + arch/parisc/kernel/syscalls/syscall.tbl | 1 + arch/powerpc/kernel/syscalls/syscall.tbl | 1 + arch/s390/kernel/syscalls/syscall.tbl | 1 + arch/sh/kernel/syscalls/syscall.tbl | 1 + arch/sparc/kernel/syscalls/syscall.tbl | 1 + arch/x86/entry/syscalls/syscall_32.tbl | 1 + arch/x86/entry/syscalls/syscall_64.tbl | 1 + arch/xtensa/kernel/syscalls/syscall.tbl | 1 + include/linux/compat.h | 12 +- include/linux/futex.h | 16 +- include/linux/sched.h | 5 +- include/uapi/asm-generic/unistd.h | 2 + include/uapi/linux/futex.h | 24 + kernel/futex/core.c | 165 ++++- kernel/futex/futex.h | 5 + kernel/futex/syscalls.c | 85 ++- kernel/sys_ni.c | 1 + scripts/syscall.tbl | 1 + .../testing/selftests/futex/functional/.gitignore | 1 + tools/testing/selftests/futex/functional/Makefile | 3 +- .../selftests/futex/functional/robust_list.c | 706 +++++++++++++++++++++ tools/testing/selftests/futex/include/logging.h | 38 ++ 29 files changed, 1026 insertions(+), 53 deletions(-) --- base-commit: 3ee84e3dd88e39b55b534e17a7b9a181f1d46809 change-id: 20250225-tonyk-robust_futex-60adeedac695
Best regards,
Create ASSERT_{EQ, NE, TRUE, FALSE} macros to make test creation easier.
Signed-off-by: André Almeida andrealmeid@igalia.com --- tools/testing/selftests/futex/include/logging.h | 38 +++++++++++++++++++++++++ 1 file changed, 38 insertions(+)
diff --git a/tools/testing/selftests/futex/include/logging.h b/tools/testing/selftests/futex/include/logging.h index 874c69ce5cce9efa3a9d6de246f5972a75437dbf..a19755622a877932884570c8f58aaee7371d5f8f 100644 --- a/tools/testing/selftests/futex/include/logging.h +++ b/tools/testing/selftests/futex/include/logging.h @@ -23,6 +23,44 @@ #include <linux/futex.h> #include "kselftest.h"
+#define ASSERT_EQ(var, value) \ +do { \ + if (var != value) { \ + ksft_test_result_fail("%s: expected %ld, but %s has %ld\n", \ + __func__, (long) value, #var, \ + (long) var); \ + return; \ + } \ +} while (0) + +#define ASSERT_NE(var, value) \ +do { \ + if (var == value) { \ + ksft_test_result_fail("%s: expected not %ld, but %s has %ld\n", \ + __func__, (long) value, #var, \ + (long) var); \ + return; \ + } \ +} while (0) + +#define ASSERT_TRUE(var) \ +do { \ + if ((var) == 0) { \ + ksft_test_result_fail("%s: expected %s to be true\n", \ + __func__, #var); \ + return; \ + } \ +} while (0) + +#define ASSERT_FALSE(var) \ +do { \ + if (var) { \ + ksft_test_result_fail("%s: expected %s to be false\n", \ + __func__, #var); \ + return; \ + } \ +} while (0) + /* * Define PASS, ERROR, and FAIL strings with and without color escape * sequences, default to no color.
Create a test for the robust list mechanism. Test the following uAPI operations:
- Creating a robust mutex where the lock waiter is wake by the kernel when the lock owner died - Setting a robust list to the current task - Getting a robust list from the current task - Getting a robust list from another task - Using the list_op_pending field from robust_list_head struct to test robustness when the lock owner dies before completing the locking - Setting a invalid size for syscall argument `len` - Adding multiple elements to a robust list wait waiting for each of them - Creating a circular list and checking that the kernel does not get stuck in an infinity loop
This is the expected output:
TAP version 13 1..7 ok 1 test_robustness ok 2 test_set_robust_list_invalid_size ok 3 test_get_robust_list_self ok 4 test_get_robust_list_child ok 5 test_set_list_op_pending ok 6 test_robust_list_multiple_elements ok 7 test_circular_list # Totals: pass:7 fail:0 xfail:0 xpass:0 skip:0 error:0
Signed-off-by: André Almeida andrealmeid@igalia.com --- .../testing/selftests/futex/functional/.gitignore | 1 + tools/testing/selftests/futex/functional/Makefile | 3 +- .../selftests/futex/functional/robust_list.c | 554 +++++++++++++++++++++ 3 files changed, 557 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/futex/functional/.gitignore b/tools/testing/selftests/futex/functional/.gitignore index 7b24ae89594a9db211d4b8469ebcef8d1f7012d8..7f447ebfbc62bbad9add0dc86a75abcdb8a4d9a7 100644 --- a/tools/testing/selftests/futex/functional/.gitignore +++ b/tools/testing/selftests/futex/functional/.gitignore @@ -11,3 +11,4 @@ futex_wait_timeout futex_wait_uninitialized_heap futex_wait_wouldblock futex_waitv +robust_list diff --git a/tools/testing/selftests/futex/functional/Makefile b/tools/testing/selftests/futex/functional/Makefile index 8cfb87f7f7c5059c82f1e6290c076d3f13f5ea41..e6fa66e622dee4de74c31c8b9b486ca01de35737 100644 --- a/tools/testing/selftests/futex/functional/Makefile +++ b/tools/testing/selftests/futex/functional/Makefile @@ -20,7 +20,8 @@ TEST_GEN_PROGS := \ futex_priv_hash \ futex_numa_mpol \ futex_waitv \ - futex_numa + futex_numa \ + robust_list
TEST_PROGS := run.sh
diff --git a/tools/testing/selftests/futex/functional/robust_list.c b/tools/testing/selftests/futex/functional/robust_list.c new file mode 100644 index 0000000000000000000000000000000000000000..42690b2440fd29a9b12c46f67f9645ccc93d1147 --- /dev/null +++ b/tools/testing/selftests/futex/functional/robust_list.c @@ -0,0 +1,554 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) 2024 Igalia S.L. + * + * Robust list test by André Almeida andrealmeid@igalia.com + * + * The robust list uAPI allows userspace to create "robust" locks, in the sense + * that if the lock holder thread dies, the remaining threads that are waiting + * for the lock won't block forever, waiting for a lock that will never be + * released. + * + * This is achieve by userspace setting a list where a thread can enter all the + * locks (futexes) that it is holding. The robust list is a linked list, and + * userspace register the start of the list with the syscall set_robust_list(). + * If such thread eventually dies, the kernel will walk this list, waking up one + * thread waiting for each futex and marking the futex word with the flag + * FUTEX_OWNER_DIED. + * + * See also + * man set_robust_list + * Documententation/locking/robust-futex-ABI.rst + * Documententation/locking/robust-futexes.rst + */ + +#define _GNU_SOURCE + +#include "futextest.h" +#include "logging.h" + +#include <errno.h> +#include <pthread.h> +#include <signal.h> +#include <stdatomic.h> +#include <stdbool.h> +#include <stddef.h> +#include <sys/mman.h> +#include <sys/wait.h> + +#define STACK_SIZE (1024 * 1024) + +#define FUTEX_TIMEOUT 3 + +static pthread_barrier_t barrier, barrier2; + +int set_robust_list(struct robust_list_head *head, size_t len) +{ + return syscall(SYS_set_robust_list, head, len); +} + +int get_robust_list(int pid, struct robust_list_head **head, size_t *len_ptr) +{ + return syscall(SYS_get_robust_list, pid, head, len_ptr); +} + +/* + * Basic lock struct, contains just the futex word and the robust list element + * Real implementations have also a *prev to easily walk in the list + */ +struct lock_struct { + _Atomic(unsigned int) futex; + struct robust_list list; +}; + +/* + * Helper function to spawn a child thread. Returns -1 on error, pid on success + */ +static int create_child(int (*fn)(void *arg), void *arg) +{ + char *stack; + pid_t pid; + + stack = mmap(NULL, STACK_SIZE, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0); + if (stack == MAP_FAILED) + return -1; + + stack += STACK_SIZE; + + pid = clone(fn, stack, CLONE_VM | SIGCHLD, arg); + + if (pid == -1) + return -1; + + return pid; +} + +/* + * Helper function to prepare and register a robust list + */ +static int set_list(struct robust_list_head *head) +{ + int ret; + + ret = set_robust_list(head, sizeof(struct robust_list_head)); + if (ret) + return ret; + + head->futex_offset = (size_t) offsetof(struct lock_struct, futex) - + (size_t) offsetof(struct lock_struct, list); + head->list.next = &head->list; + head->list_op_pending = NULL; + + return 0; +} + +/* + * A basic (and incomplete) mutex lock function with robustness + */ +static int mutex_lock(struct lock_struct *lock, struct robust_list_head *head, bool error_inject) +{ + _Atomic(unsigned int) *futex = &lock->futex; + unsigned int zero = 0; + int ret = -1; + pid_t tid = gettid(); + + /* + * Set list_op_pending before starting the lock, so the kernel can catch + * the case where the thread died during the lock operation + */ + head->list_op_pending = &lock->list; + + if (atomic_compare_exchange_strong(futex, &zero, tid)) { + /* + * We took the lock, insert it in the robust list + */ + struct robust_list *list = &head->list; + + /* Error injection to test list_op_pending */ + if (error_inject) + return 0; + + while (list->next != &head->list) + list = list->next; + + list->next = &lock->list; + lock->list.next = &head->list; + + ret = 0; + } else { + /* + * We didn't take the lock, wait until the owner wakes (or dies) + */ + struct timespec to; + + to.tv_sec = FUTEX_TIMEOUT; + to.tv_nsec = 0; + + tid = atomic_load(futex); + /* Kernel ignores futexes without the waiters flag */ + tid |= FUTEX_WAITERS; + atomic_store(futex, tid); + + ret = futex_wait((futex_t *) futex, tid, &to, 0); + + /* + * A real mutex_lock() implementation would loop here to finally + * take the lock. We don't care about that, so we stop here. + */ + } + + head->list_op_pending = NULL; + + return ret; +} + +/* + * This child thread will succeed taking the lock, and then will exit holding it + */ +static int child_fn_lock(void *arg) +{ + struct lock_struct *lock = (struct lock_struct *) arg; + struct robust_list_head head; + int ret; + + ret = set_list(&head); + if (ret) + ksft_test_result_fail("set_robust_list error\n"); + + ret = mutex_lock(lock, &head, false); + if (ret) + ksft_test_result_fail("mutex_lock error\n"); + + pthread_barrier_wait(&barrier); + + /* + * There's a race here: the parent thread needs to be inside + * futex_wait() before the child thread dies, otherwise it will miss the + * wakeup from handle_futex_death() that this child will emit. We wait a + * little bit just to make sure that this happens. + */ + sleep(1); + + return 0; +} + +/* + * Spawns a child thread that will set a robust list, take the lock, register it + * in the robust list and die. The parent thread will wait on this futex, and + * should be waken up when the child exits. + */ +static void test_robustness(void) +{ + struct lock_struct lock = { .futex = 0 }; + struct robust_list_head head; + _Atomic(unsigned int) *futex = &lock.futex; + int ret; + + ret = set_list(&head); + ASSERT_EQ(ret, 0); + + /* + * Lets use a barrier to ensure that the child thread takes the lock + * before the parent + */ + ret = pthread_barrier_init(&barrier, NULL, 2); + ASSERT_EQ(ret, 0); + + ret = create_child(&child_fn_lock, &lock); + ASSERT_NE(ret, -1); + + pthread_barrier_wait(&barrier); + ret = mutex_lock(&lock, &head, false); + + /* + * futex_wait() should return 0 and the futex word should be marked with + * FUTEX_OWNER_DIED + */ + ASSERT_EQ(ret, 0); + if (ret != 0) + printf("futex wait returned %d", errno); + + ASSERT_TRUE(*futex | FUTEX_OWNER_DIED); + + wait(NULL); + pthread_barrier_destroy(&barrier); + + ksft_test_result_pass("%s\n", __func__); +} + +/* + * The only valid value for len is sizeof(*head) + */ +static void test_set_robust_list_invalid_size(void) +{ + struct robust_list_head head; + size_t head_size = sizeof(struct robust_list_head); + int ret; + + ret = set_robust_list(&head, head_size); + ASSERT_EQ(ret, 0); + + ret = set_robust_list(&head, head_size * 2); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, EINVAL); + + ret = set_robust_list(&head, head_size - 1); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, EINVAL); + + ret = set_robust_list(&head, 0); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, EINVAL); + + ksft_test_result_pass("%s\n", __func__); +} + +/* + * Test get_robust_list with pid = 0, getting the list of the running thread + */ +static void test_get_robust_list_self(void) +{ + struct robust_list_head head, head2, *get_head; + size_t head_size = sizeof(struct robust_list_head), len_ptr; + int ret; + + ret = set_robust_list(&head, head_size); + ASSERT_EQ(ret, 0); + + ret = get_robust_list(0, &get_head, &len_ptr); + ASSERT_EQ(ret, 0); + ASSERT_EQ(get_head, &head); + ASSERT_EQ(head_size, len_ptr); + + ret = set_robust_list(&head2, head_size); + ASSERT_EQ(ret, 0); + + ret = get_robust_list(0, &get_head, &len_ptr); + ASSERT_EQ(ret, 0); + ASSERT_EQ(get_head, &head2); + ASSERT_EQ(head_size, len_ptr); + + ksft_test_result_pass("%s\n", __func__); +} + +static int child_list(void *arg) +{ + struct robust_list_head *head = (struct robust_list_head *) arg; + int ret; + + ret = set_robust_list(head, sizeof(struct robust_list_head)); + if (ret) + ksft_test_result_fail("set_robust_list error\n"); + + pthread_barrier_wait(&barrier); + pthread_barrier_wait(&barrier2); + + return 0; +} + +/* + * Test get_robust_list from another thread. We use two barriers here to ensure + * that: + * 1) the child thread set the list before we try to get it from the + * parent + * 2) the child thread still alive when we try to get the list from it + */ +static void test_get_robust_list_child(void) +{ + pid_t tid; + int ret; + struct robust_list_head head, *get_head; + size_t len_ptr; + + ret = pthread_barrier_init(&barrier, NULL, 2); + ret = pthread_barrier_init(&barrier2, NULL, 2); + ASSERT_EQ(ret, 0); + + tid = create_child(&child_list, &head); + ASSERT_NE(tid, -1); + + pthread_barrier_wait(&barrier); + + ret = get_robust_list(tid, &get_head, &len_ptr); + ASSERT_EQ(ret, 0); + ASSERT_EQ(&head, get_head); + + pthread_barrier_wait(&barrier2); + + wait(NULL); + pthread_barrier_destroy(&barrier); + pthread_barrier_destroy(&barrier2); + + ksft_test_result_pass("%s\n", __func__); +} + +static int child_fn_lock_with_error(void *arg) +{ + struct lock_struct *lock = (struct lock_struct *) arg; + struct robust_list_head head; + int ret; + + ret = set_list(&head); + if (ret) + ksft_test_result_fail("set_robust_list error\n"); + + ret = mutex_lock(lock, &head, true); + if (ret) + ksft_test_result_fail("mutex_lock error\n"); + + pthread_barrier_wait(&barrier); + + sleep(1); + + return 0; +} + +/* + * Same as robustness test, but inject an error where the mutex_lock() exits + * earlier, just after setting list_op_pending and taking the lock, to test the + * list_op_pending mechanism + */ +static void test_set_list_op_pending(void) +{ + struct lock_struct lock = { .futex = 0 }; + struct robust_list_head head; + _Atomic(unsigned int) *futex = &lock.futex; + int ret; + + ret = set_list(&head); + ASSERT_EQ(ret, 0); + + ret = pthread_barrier_init(&barrier, NULL, 2); + ASSERT_EQ(ret, 0); + + ret = create_child(&child_fn_lock_with_error, &lock); + ASSERT_NE(ret, -1); + + pthread_barrier_wait(&barrier); + ret = mutex_lock(&lock, &head, false); + + ASSERT_EQ(ret, 0); + if (ret != 0) + printf("futex wait returned %d", errno); + + ASSERT_TRUE(*futex | FUTEX_OWNER_DIED); + + wait(NULL); + pthread_barrier_destroy(&barrier); + + ksft_test_result_pass("%s\n", __func__); +} + +#define CHILD_NR 10 + +static int child_lock_holder(void *arg) +{ + struct lock_struct *locks = (struct lock_struct *) arg; + struct robust_list_head head; + int i; + + set_list(&head); + + for (i = 0; i < CHILD_NR; i++) { + locks[i].futex = 0; + mutex_lock(&locks[i], &head, false); + } + + pthread_barrier_wait(&barrier); + pthread_barrier_wait(&barrier2); + + sleep(1); + return 0; +} + +static int child_wait_lock(void *arg) +{ + struct lock_struct *lock = (struct lock_struct *) arg; + struct robust_list_head head; + int ret; + + pthread_barrier_wait(&barrier2); + ret = mutex_lock(lock, &head, false); + + if (ret) + ksft_test_result_fail("mutex_lock error\n"); + + if (!(lock->futex | FUTEX_OWNER_DIED)) + ksft_test_result_fail("futex not marked with FUTEX_OWNER_DIED\n"); + + return 0; +} + +/* + * Test a robust list of more than one element. All the waiters should wake when + * the holder dies + */ +static void test_robust_list_multiple_elements(void) +{ + struct lock_struct locks[CHILD_NR]; + int i, ret; + + ret = pthread_barrier_init(&barrier, NULL, 2); + ASSERT_EQ(ret, 0); + ret = pthread_barrier_init(&barrier2, NULL, CHILD_NR + 1); + ASSERT_EQ(ret, 0); + + create_child(&child_lock_holder, &locks); + + /* Wait until the locker thread takes the look */ + pthread_barrier_wait(&barrier); + + for (i = 0; i < CHILD_NR; i++) + create_child(&child_wait_lock, &locks[i]); + + /* Wait for all children to return */ + while (wait(NULL) > 0); + + pthread_barrier_destroy(&barrier); + pthread_barrier_destroy(&barrier2); + + ksft_test_result_pass("%s\n", __func__); +} + +static int child_circular_list(void *arg) +{ + static struct robust_list_head head; + struct lock_struct a, b, c; + int ret; + + ret = set_list(&head); + if (ret) + ksft_test_result_fail("set_list error\n"); + + head.list.next = &a.list; + + /* + * The last element should point to head list, but we short circuit it + */ + a.list.next = &b.list; + b.list.next = &c.list; + c.list.next = &a.list; + + return 0; +} + +/* + * Create a circular robust list. The kernel should be able to destroy the list + * while processing it so it won't be trapped in an infinite loop while handling + * a process exit + */ +static void test_circular_list(void) +{ + create_child(child_circular_list, NULL); + + wait(NULL); + + ksft_test_result_pass("%s\n", __func__); +} + +void usage(char *prog) +{ + printf("Usage: %s\n", prog); + printf(" -c Use color\n"); + printf(" -h Display this help message\n"); + printf(" -v L Verbosity level: %d=QUIET %d=CRITICAL %d=INFO\n", + VQUIET, VCRITICAL, VINFO); +} + +int main(int argc, char *argv[]) +{ + int c; + + while ((c = getopt(argc, argv, "cht:v:")) != -1) { + switch (c) { + case 'c': + log_color(1); + break; + case 'h': + usage(basename(argv[0])); + exit(0); + case 'v': + log_verbosity(atoi(optarg)); + break; + default: + usage(basename(argv[0])); + exit(1); + } + } + + ksft_print_header(); + ksft_set_plan(7); + + test_robustness(); + + test_set_robust_list_invalid_size(); + test_get_robust_list_self(); + test_get_robust_list_child(); + test_set_list_op_pending(); + test_robust_list_multiple_elements(); + test_circular_list(); + + ksft_print_cnts(); + return 0; +}
There are two functions for handling robust lists during the task exit: exit_robust_list() and compat_exit_robust_list(). The first one handles either 64bit or 32bit lists, depending if it's a 64bit or 32bit kernel. The compat_exit_robust_list() only exists in 64bit kernels that supports 32bit syscalls, and handles 32bit lists.
For the new syscall set_robust_list2(), 64bit kernels need to be able to handle 32bit lists despite having or not support for 32bit syscalls, so make compat_exit_robust_list() exist regardless of compat_ config.
Also, use explicitly sizing, otherwise in a 32bit kernel both exit_robust_list() and compat_exit_robust_list() would be the exactly same function, with none of them dealing with 64bit robust lists.
Signed-off-by: André Almeida andrealmeid@igalia.com --- include/linux/compat.h | 12 +----------- include/linux/futex.h | 11 +++++++++++ include/linux/sched.h | 2 +- kernel/futex/core.c | 44 ++++++++++++++++++++++++++++---------------- kernel/futex/syscalls.c | 4 ++-- 5 files changed, 43 insertions(+), 30 deletions(-)
diff --git a/include/linux/compat.h b/include/linux/compat.h index 56cebaff0c910fda853a0e2b3d6d0517e55f8b38..968a9135ff486cf9c8be2a18b80cd4c46e890236 100644 --- a/include/linux/compat.h +++ b/include/linux/compat.h @@ -385,16 +385,6 @@ struct compat_ifconf { compat_caddr_t ifcbuf; };
-struct compat_robust_list { - compat_uptr_t next; -}; - -struct compat_robust_list_head { - struct compat_robust_list list; - compat_long_t futex_offset; - compat_uptr_t list_op_pending; -}; - #ifdef CONFIG_COMPAT_OLD_SIGACTION struct compat_old_sigaction { compat_uptr_t sa_handler; @@ -672,7 +662,7 @@ asmlinkage long compat_sys_waitid(int, compat_pid_t, struct compat_siginfo __user *, int, struct compat_rusage __user *); asmlinkage long -compat_sys_set_robust_list(struct compat_robust_list_head __user *head, +compat_sys_set_robust_list(struct robust_list_head32 __user *head, compat_size_t len); asmlinkage long compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr, diff --git a/include/linux/futex.h b/include/linux/futex.h index 168ffd5996b4808491c05bdc7c8d0aeca1d37ee5..cd7c5d12c846566c56f3f3ea74b95e437a6e8193 100644 --- a/include/linux/futex.h +++ b/include/linux/futex.h @@ -56,6 +56,17 @@ union futex_key { #define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = 0ULL } }
#ifdef CONFIG_FUTEX + +struct robust_list32 { + u32 next; +}; + +struct robust_list_head32 { + struct robust_list32 list; + s32 futex_offset; + u32 list_op_pending; +}; + enum { FUTEX_STATE_OK, FUTEX_STATE_EXITING, diff --git a/include/linux/sched.h b/include/linux/sched.h index 45e5953b8f326c2ff5e19de469d6cba27cc4c17d..51e5d05a9fcd407dcd53b7b7cb8c59783660a826 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1324,7 +1324,7 @@ struct task_struct { #ifdef CONFIG_FUTEX struct robust_list_head __user *robust_list; #ifdef CONFIG_COMPAT - struct compat_robust_list_head __user *compat_robust_list; + struct robust_list_head32 __user *compat_robust_list; #endif struct list_head pi_state_list; struct futex_pi_state *pi_state_cache; diff --git a/kernel/futex/core.c b/kernel/futex/core.c index 19a2c65f3d373c0b60c864a6fe0604787221d342..8640770aadc611b7341a3abb41bdb740e6394479 100644 --- a/kernel/futex/core.c +++ b/kernel/futex/core.c @@ -1144,13 +1144,14 @@ static inline int fetch_robust_entry(struct robust_list __user **entry, return 0; }
+#ifdef CONFIG_64BIT /* * Walk curr->robust_list (very carefully, it's a userspace list!) * and mark any locks found there dead, and notify any waiters. * * We silently return on any sign of list-walking problem. */ -static void exit_robust_list(struct task_struct *curr) +static void exit_robust_list64(struct task_struct *curr) { struct robust_list_head __user *head = curr->robust_list; struct robust_list __user *entry, *next_entry, *pending; @@ -1211,8 +1212,13 @@ static void exit_robust_list(struct task_struct *curr) curr, pip, HANDLE_DEATH_PENDING); } } +#else +static void exit_robust_list64(struct task_struct *curr) +{ + pr_warn("32bit kernel should not allow ROBUST_LIST_64BIT"); +} +#endif
-#ifdef CONFIG_COMPAT static void __user *futex_uaddr(struct robust_list __user *entry, compat_long_t futex_offset) { @@ -1226,13 +1232,13 @@ static void __user *futex_uaddr(struct robust_list __user *entry, * Fetch a robust-list pointer. Bit 0 signals PI futexes: */ static inline int -compat_fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry, - compat_uptr_t __user *head, unsigned int *pi) +fetch_robust_entry32(u32 *uentry, struct robust_list __user **entry, + u32 __user *head, unsigned int *pi) { if (get_user(*uentry, head)) return -EFAULT;
- *entry = compat_ptr((*uentry) & ~1); + *entry = (void __user *)(unsigned long)((*uentry) & ~1); *pi = (unsigned int)(*uentry) & 1;
return 0; @@ -1244,21 +1250,21 @@ compat_fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **ent * * We silently return on any sign of list-walking problem. */ -static void compat_exit_robust_list(struct task_struct *curr) +static void exit_robust_list32(struct task_struct *curr) { - struct compat_robust_list_head __user *head = curr->compat_robust_list; + struct robust_list_head32 __user *head = curr->compat_robust_list; struct robust_list __user *entry, *next_entry, *pending; unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; unsigned int next_pi; - compat_uptr_t uentry, next_uentry, upending; - compat_long_t futex_offset; + u32 uentry, next_uentry, upending; + s32 futex_offset; int rc;
/* * Fetch the list head (which was registered earlier, via * sys_set_robust_list()): */ - if (compat_fetch_robust_entry(&uentry, &entry, &head->list.next, &pi)) + if (fetch_robust_entry32((u32 *)&uentry, &entry, (u32 *)&head->list.next, &pi)) return; /* * Fetch the relative futex offset: @@ -1269,7 +1275,7 @@ static void compat_exit_robust_list(struct task_struct *curr) * Fetch any possibly pending lock-add first, and handle it * if it exists: */ - if (compat_fetch_robust_entry(&upending, &pending, + if (fetch_robust_entry32(&upending, &pending, &head->list_op_pending, &pip)) return;
@@ -1279,8 +1285,8 @@ static void compat_exit_robust_list(struct task_struct *curr) * Fetch the next entry in the list before calling * handle_futex_death: */ - rc = compat_fetch_robust_entry(&next_uentry, &next_entry, - (compat_uptr_t __user *)&entry->next, &next_pi); + rc = fetch_robust_entry32(&next_uentry, &next_entry, + (u32 __user *)&entry->next, &next_pi); /* * A pending lock might already be on the list, so * dont process it twice: @@ -1311,7 +1317,6 @@ static void compat_exit_robust_list(struct task_struct *curr) handle_futex_death(uaddr, curr, pip, HANDLE_DEATH_PENDING); } } -#endif
#ifdef CONFIG_FUTEX_PI
@@ -1406,14 +1411,21 @@ static inline void exit_pi_state_list(struct task_struct *curr) { }
static void futex_cleanup(struct task_struct *tsk) { +#ifdef CONFIG_64BIT if (unlikely(tsk->robust_list)) { - exit_robust_list(tsk); + exit_robust_list64(tsk); tsk->robust_list = NULL; } +#else + if (unlikely(tsk->robust_list)) { + exit_robust_list32(tsk); + tsk->robust_list = NULL; + } +#endif
#ifdef CONFIG_COMPAT if (unlikely(tsk->compat_robust_list)) { - compat_exit_robust_list(tsk); + exit_robust_list32(tsk); tsk->compat_robust_list = NULL; } #endif diff --git a/kernel/futex/syscalls.c b/kernel/futex/syscalls.c index 4b6da9116aa6c33db9796e3055ce0c90b02d7b91..dba193dfd216cc929c8f4d979aa2bcd99237e2d8 100644 --- a/kernel/futex/syscalls.c +++ b/kernel/futex/syscalls.c @@ -440,7 +440,7 @@ SYSCALL_DEFINE4(futex_requeue,
#ifdef CONFIG_COMPAT COMPAT_SYSCALL_DEFINE2(set_robust_list, - struct compat_robust_list_head __user *, head, + struct robust_list_head32 __user *, head, compat_size_t, len) { if (unlikely(len != sizeof(*head))) @@ -455,7 +455,7 @@ COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid, compat_uptr_t __user *, head_ptr, compat_size_t __user *, len_ptr) { - struct compat_robust_list_head __user *head; + struct robust_list_head32 __user *head; unsigned long ret; struct task_struct *p;
Hi André,
kernel test robot noticed the following build warnings:
[auto build test WARNING on 3ee84e3dd88e39b55b534e17a7b9a181f1d46809]
url: https://github.com/intel-lab-lkp/linux/commits/Andr-Almeida/selftests-futex-... base: 3ee84e3dd88e39b55b534e17a7b9a181f1d46809 patch link: https://lore.kernel.org/r/20250520-tonyk-robust_futex-v4-3-1123093e59de%40ig... patch subject: [PATCH v4 3/7] futex: Use explicit sizes for compat_exit_robust_list config: arm-randconfig-002-20250521 (https://download.01.org/0day-ci/archive/20250521/202505212147.5qoTgcmU-lkp@i...) compiler: clang version 21.0.0git (https://github.com/llvm/llvm-project f819f46284f2a79790038e1f6649172789734ae8) reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250521/202505212147.5qoTgcmU-lkp@i...)
If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot lkp@intel.com | Closes: https://lore.kernel.org/oe-kbuild-all/202505212147.5qoTgcmU-lkp@intel.com/
All warnings (new ones prefixed by >>):
In file included from io_uring/notif.c:9: In file included from io_uring/notif.h:5: In file included from include/net/sock.h:46: In file included from include/linux/netdevice.h:44: In file included from include/uapi/linux/neighbour.h:6: In file included from include/linux/netlink.h:9: In file included from include/net/scm.h:13: In file included from include/net/compat.h:8:
include/linux/compat.h:665:35: warning: declaration of 'struct robust_list_head32' will not be visible outside of this function [-Wvisibility]
665 | compat_sys_set_robust_list(struct robust_list_head32 __user *head, | ^ 1 warning generated. -- In file included from io_uring/uring_cmd.c:9: In file included from include/net/sock.h:46: In file included from include/linux/netdevice.h:44: In file included from include/uapi/linux/neighbour.h:6: In file included from include/linux/netlink.h:9: In file included from include/net/scm.h:13: In file included from include/net/compat.h:8:
include/linux/compat.h:665:35: warning: declaration of 'struct robust_list_head32' will not be visible outside of this function [-Wvisibility]
665 | compat_sys_set_robust_list(struct robust_list_head32 __user *head, | ^ io_uring/uring_cmd.c:311:19: warning: unused function 'io_uring_cmd_getsockopt' [-Wunused-function] 311 | static inline int io_uring_cmd_getsockopt(struct socket *sock, | ^~~~~~~~~~~~~~~~~~~~~~~ io_uring/uring_cmd.c:338:19: warning: unused function 'io_uring_cmd_setsockopt' [-Wunused-function] 338 | static inline int io_uring_cmd_setsockopt(struct socket *sock, | ^~~~~~~~~~~~~~~~~~~~~~~ 3 warnings generated.
vim +665 include/linux/compat.h
621 622 #ifdef __ARCH_WANT_COMPAT_SYS_PWRITEV64 623 asmlinkage long compat_sys_pwritev64(unsigned long fd, 624 const struct iovec __user *vec, 625 unsigned long vlen, loff_t pos); 626 #endif 627 asmlinkage long compat_sys_sendfile(int out_fd, int in_fd, 628 compat_off_t __user *offset, compat_size_t count); 629 asmlinkage long compat_sys_sendfile64(int out_fd, int in_fd, 630 compat_loff_t __user *offset, compat_size_t count); 631 asmlinkage long compat_sys_pselect6_time32(int n, compat_ulong_t __user *inp, 632 compat_ulong_t __user *outp, 633 compat_ulong_t __user *exp, 634 struct old_timespec32 __user *tsp, 635 void __user *sig); 636 asmlinkage long compat_sys_pselect6_time64(int n, compat_ulong_t __user *inp, 637 compat_ulong_t __user *outp, 638 compat_ulong_t __user *exp, 639 struct __kernel_timespec __user *tsp, 640 void __user *sig); 641 asmlinkage long compat_sys_ppoll_time32(struct pollfd __user *ufds, 642 unsigned int nfds, 643 struct old_timespec32 __user *tsp, 644 const compat_sigset_t __user *sigmask, 645 compat_size_t sigsetsize); 646 asmlinkage long compat_sys_ppoll_time64(struct pollfd __user *ufds, 647 unsigned int nfds, 648 struct __kernel_timespec __user *tsp, 649 const compat_sigset_t __user *sigmask, 650 compat_size_t sigsetsize); 651 asmlinkage long compat_sys_signalfd4(int ufd, 652 const compat_sigset_t __user *sigmask, 653 compat_size_t sigsetsize, int flags); 654 asmlinkage long compat_sys_newfstatat(unsigned int dfd, 655 const char __user *filename, 656 struct compat_stat __user *statbuf, 657 int flag); 658 asmlinkage long compat_sys_newfstat(unsigned int fd, 659 struct compat_stat __user *statbuf); 660 /* No generic prototype for sync_file_range and sync_file_range2 */ 661 asmlinkage long compat_sys_waitid(int, compat_pid_t, 662 struct compat_siginfo __user *, int, 663 struct compat_rusage __user *); 664 asmlinkage long
665 compat_sys_set_robust_list(struct robust_list_head32 __user *head,
666 compat_size_t len); 667 asmlinkage long 668 compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr, 669 compat_size_t __user *len_ptr); 670 asmlinkage long compat_sys_getitimer(int which, 671 struct old_itimerval32 __user *it); 672 asmlinkage long compat_sys_setitimer(int which, 673 struct old_itimerval32 __user *in, 674 struct old_itimerval32 __user *out); 675 asmlinkage long compat_sys_kexec_load(compat_ulong_t entry, 676 compat_ulong_t nr_segments, 677 struct compat_kexec_segment __user *, 678 compat_ulong_t flags); 679 asmlinkage long compat_sys_timer_create(clockid_t which_clock, 680 struct compat_sigevent __user *timer_event_spec, 681 timer_t __user *created_timer_id); 682 asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid, 683 compat_long_t addr, compat_long_t data); 684 asmlinkage long compat_sys_sched_setaffinity(compat_pid_t pid, 685 unsigned int len, 686 compat_ulong_t __user *user_mask_ptr); 687 asmlinkage long compat_sys_sched_getaffinity(compat_pid_t pid, 688 unsigned int len, 689 compat_ulong_t __user *user_mask_ptr); 690 asmlinkage long compat_sys_sigaltstack(const compat_stack_t __user *uss_ptr, 691 compat_stack_t __user *uoss_ptr); 692 asmlinkage long compat_sys_rt_sigsuspend(compat_sigset_t __user *unewset, 693 compat_size_t sigsetsize); 694 #ifndef CONFIG_ODD_RT_SIGACTION 695 asmlinkage long compat_sys_rt_sigaction(int, 696 const struct compat_sigaction __user *, 697 struct compat_sigaction __user *, 698 compat_size_t); 699 #endif 700 asmlinkage long compat_sys_rt_sigprocmask(int how, compat_sigset_t __user *set, 701 compat_sigset_t __user *oset, 702 compat_size_t sigsetsize); 703 asmlinkage long compat_sys_rt_sigpending(compat_sigset_t __user *uset, 704 compat_size_t sigsetsize); 705 asmlinkage long compat_sys_rt_sigtimedwait_time32(compat_sigset_t __user *uthese, 706 struct compat_siginfo __user *uinfo, 707 struct old_timespec32 __user *uts, compat_size_t sigsetsize); 708 asmlinkage long compat_sys_rt_sigtimedwait_time64(compat_sigset_t __user *uthese, 709 struct compat_siginfo __user *uinfo, 710 struct __kernel_timespec __user *uts, compat_size_t sigsetsize); 711 asmlinkage long compat_sys_rt_sigqueueinfo(compat_pid_t pid, int sig, 712 struct compat_siginfo __user *uinfo); 713 /* No generic prototype for rt_sigreturn */ 714 asmlinkage long compat_sys_times(struct compat_tms __user *tbuf); 715 asmlinkage long compat_sys_getrlimit(unsigned int resource, 716 struct compat_rlimit __user *rlim); 717 asmlinkage long compat_sys_setrlimit(unsigned int resource, 718 struct compat_rlimit __user *rlim); 719 asmlinkage long compat_sys_getrusage(int who, struct compat_rusage __user *ru); 720 asmlinkage long compat_sys_gettimeofday(struct old_timeval32 __user *tv, 721 struct timezone __user *tz); 722 asmlinkage long compat_sys_settimeofday(struct old_timeval32 __user *tv, 723 struct timezone __user *tz); 724 asmlinkage long compat_sys_sysinfo(struct compat_sysinfo __user *info); 725 asmlinkage long compat_sys_mq_open(const char __user *u_name, 726 int oflag, compat_mode_t mode, 727 struct compat_mq_attr __user *u_attr); 728 asmlinkage long compat_sys_mq_notify(mqd_t mqdes, 729 const struct compat_sigevent __user *u_notification); 730 asmlinkage long compat_sys_mq_getsetattr(mqd_t mqdes, 731 const struct compat_mq_attr __user *u_mqstat, 732 struct compat_mq_attr __user *u_omqstat); 733 asmlinkage long compat_sys_msgctl(int first, int second, void __user *uptr); 734 asmlinkage long compat_sys_msgrcv(int msqid, compat_uptr_t msgp, 735 compat_ssize_t msgsz, compat_long_t msgtyp, int msgflg); 736 asmlinkage long compat_sys_msgsnd(int msqid, compat_uptr_t msgp, 737 compat_ssize_t msgsz, int msgflg); 738 asmlinkage long compat_sys_semctl(int semid, int semnum, int cmd, int arg); 739 asmlinkage long compat_sys_shmctl(int first, int second, void __user *uptr); 740 asmlinkage long compat_sys_shmat(int shmid, compat_uptr_t shmaddr, int shmflg); 741 asmlinkage long compat_sys_recvfrom(int fd, void __user *buf, compat_size_t len, 742 unsigned flags, struct sockaddr __user *addr, 743 int __user *addrlen); 744 asmlinkage long compat_sys_sendmsg(int fd, struct compat_msghdr __user *msg, 745 unsigned flags); 746 asmlinkage long compat_sys_recvmsg(int fd, struct compat_msghdr __user *msg, 747 unsigned int flags); 748 /* No generic prototype for readahead */ 749 asmlinkage long compat_sys_keyctl(u32 option, 750 u32 arg2, u32 arg3, u32 arg4, u32 arg5); 751 asmlinkage long compat_sys_execve(const char __user *filename, const compat_uptr_t __user *argv, 752 const compat_uptr_t __user *envp); 753 /* No generic prototype for fadvise64_64 */ 754 /* CONFIG_MMU only */ 755 asmlinkage long compat_sys_rt_tgsigqueueinfo(compat_pid_t tgid, 756 compat_pid_t pid, int sig, 757 struct compat_siginfo __user *uinfo); 758 asmlinkage long compat_sys_recvmmsg_time64(int fd, struct compat_mmsghdr __user *mmsg, 759 unsigned vlen, unsigned int flags, 760 struct __kernel_timespec __user *timeout); 761 asmlinkage long compat_sys_recvmmsg_time32(int fd, struct compat_mmsghdr __user *mmsg, 762 unsigned vlen, unsigned int flags, 763 struct old_timespec32 __user *timeout); 764 asmlinkage long compat_sys_wait4(compat_pid_t pid, 765 compat_uint_t __user *stat_addr, int options, 766 struct compat_rusage __user *ru); 767 asmlinkage long compat_sys_fanotify_mark(int, unsigned int, __u32, __u32, 768 int, const char __user *); 769 asmlinkage long compat_sys_open_by_handle_at(int mountdirfd, 770 struct file_handle __user *handle, 771 int flags); 772 asmlinkage long compat_sys_sendmmsg(int fd, struct compat_mmsghdr __user *mmsg, 773 unsigned vlen, unsigned int flags); 774 asmlinkage long compat_sys_execveat(int dfd, const char __user *filename, 775 const compat_uptr_t __user *argv, 776 const compat_uptr_t __user *envp, int flags); 777 asmlinkage ssize_t compat_sys_preadv2(compat_ulong_t fd, 778 const struct iovec __user *vec, 779 compat_ulong_t vlen, u32 pos_low, u32 pos_high, rwf_t flags); 780 asmlinkage ssize_t compat_sys_pwritev2(compat_ulong_t fd, 781 const struct iovec __user *vec, 782 compat_ulong_t vlen, u32 pos_low, u32 pos_high, rwf_t flags); 783 #ifdef __ARCH_WANT_COMPAT_SYS_PREADV64V2 784 asmlinkage long compat_sys_preadv64v2(unsigned long fd, 785 const struct iovec __user *vec, 786 unsigned long vlen, loff_t pos, rwf_t flags); 787 #endif 788
Create a new robust_list() syscall. The current syscall can't be expanded to cover the following use case, so a new one is needed. This new syscall allows users to set multiple robust lists per process and to have either 32bit or 64bit pointers in the list.
* Interface
This is the proposed interface:
long set_robust_list2(void *head, int index, unsigned int flags)
`head` is the head of the userspace struct robust_list_head, just as old set_robust_list(). It needs to be a void pointer since it can point to a normal robust_list_head or a compat_robust_list_head.
`flags` can be used for defining the list type:
enum robust_list_type { ROBUST_LIST_32BIT, ROBUST_LIST_64BIT, };
`index` is the index in the internal robust_list's linked list (the naming starts to get confusing, I reckon). If `index == -1`, that means that user wants to set a new robust_list, and the kernel will append it in the end of the list, assign a new index and return this index to the user. If `index >= 0`, that means that user wants to re-set `*head` of an already existing list (similarly to what happens when you call set_robust_list() twice with different `*head`).
If `index` is out of range, or it points to a non-existing robust_list, or if the internal list is full, an error is returned.
Unaligned `head` addresses are refused by the kernel with -EINVAL.
User cannot remove lists.
* Implementation
The old syscall's set/get_robust_list() are converted to use the linked list as well. When using only the old syscalls user shouldn't any difference as the internal code will handle the linked list insertion as usual. When mixing old and new interfaces users should be aware that one of the elements of the list was created by another syscall and they should have special care handling this element index.
On exit, the linked list is parsed and all robust lists regardless of which interface it was used to create them are handled.
Signed-off-by: André Almeida andrealmeid@igalia.com --- include/linux/futex.h | 5 +- include/linux/sched.h | 5 +- include/uapi/asm-generic/unistd.h | 2 + include/uapi/linux/futex.h | 24 +++++++++ kernel/futex/core.c | 111 ++++++++++++++++++++++++++++++-------- kernel/futex/futex.h | 5 ++ kernel/futex/syscalls.c | 81 ++++++++++++++++++++++++++-- 7 files changed, 204 insertions(+), 29 deletions(-)
diff --git a/include/linux/futex.h b/include/linux/futex.h index cd7c5d12c846566c56f3f3ea74b95e437a6e8193..7721629926535c775bd7b05b5283a3d0b51262d6 100644 --- a/include/linux/futex.h +++ b/include/linux/futex.h @@ -75,10 +75,11 @@ enum {
static inline void futex_init_task(struct task_struct *tsk) { - tsk->robust_list = NULL; + tsk->robust_list_index = -1; #ifdef CONFIG_COMPAT - tsk->compat_robust_list = NULL; + tsk->compat_robust_list_index = -1; #endif + INIT_LIST_HEAD(&tsk->robust_list2); INIT_LIST_HEAD(&tsk->pi_state_list); tsk->pi_state_cache = NULL; tsk->futex_state = FUTEX_STATE_OK; diff --git a/include/linux/sched.h b/include/linux/sched.h index 51e5d05a9fcd407dcd53b7b7cb8c59783660a826..a37c55cf0a4d942ec1fbedb8bcd4be5a3ebb20bb 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1322,10 +1322,11 @@ struct task_struct { u32 rmid; #endif #ifdef CONFIG_FUTEX - struct robust_list_head __user *robust_list; + int robust_list_index; #ifdef CONFIG_COMPAT - struct robust_list_head32 __user *compat_robust_list; + int compat_robust_list_index; #endif + struct list_head robust_list2; struct list_head pi_state_list; struct futex_pi_state *pi_state_cache; struct mutex futex_exit_mutex; diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h index 2892a45023af6d3eb941623d4fed04841ab07e02..ebe68c2c88eb5390dda184ce9268a8d3a606c9e5 100644 --- a/include/uapi/asm-generic/unistd.h +++ b/include/uapi/asm-generic/unistd.h @@ -852,6 +852,8 @@ __SYSCALL(__NR_removexattrat, sys_removexattrat) #define __NR_open_tree_attr 467 __SYSCALL(__NR_open_tree_attr, sys_open_tree_attr)
+#define __NR_set_robust_list2 467 + #undef __NR_syscalls #define __NR_syscalls 468
diff --git a/include/uapi/linux/futex.h b/include/uapi/linux/futex.h index 7e2744ec89336a260e89883e95222eda199eeb7f..cbd321eca03afb6bdcf47e9534761d82f9de7e43 100644 --- a/include/uapi/linux/futex.h +++ b/include/uapi/linux/futex.h @@ -153,6 +153,30 @@ struct robust_list_head { struct robust_list __user *list_op_pending; };
+#define ROBUST_LISTS_PER_TASK 10 + +enum robust_list2_type { + ROBUST_LIST_32BIT, + ROBUST_LIST_64BIT, +}; + +#define ROBUST_LIST_TYPE_MASK (ROBUST_LIST_32BIT | ROBUST_LIST_64BIT) + +/* + * This is an entry of a linked list of robust lists. + * + * @head: can point to a 64bit list or a 32bit list + * @list_type: determine the size of the futex pointers in the list + * @index: the index of this entry in the list + * @list: linked list element + */ +struct robust_list2_entry { + void __user *head; + enum robust_list2_type list_type; + unsigned int index; + struct list_head list; +}; + /* * Are there any waiters for this robust futex: */ diff --git a/kernel/futex/core.c b/kernel/futex/core.c index 8640770aadc611b7341a3abb41bdb740e6394479..49b3bc592948a811f995017027f33ad8f285531f 100644 --- a/kernel/futex/core.c +++ b/kernel/futex/core.c @@ -1151,9 +1151,9 @@ static inline int fetch_robust_entry(struct robust_list __user **entry, * * We silently return on any sign of list-walking problem. */ -static void exit_robust_list64(struct task_struct *curr) +static void exit_robust_list64(struct task_struct *curr, + struct robust_list_head __user *head) { - struct robust_list_head __user *head = curr->robust_list; struct robust_list __user *entry, *next_entry, *pending; unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; unsigned int next_pi; @@ -1213,7 +1213,8 @@ static void exit_robust_list64(struct task_struct *curr) } } #else -static void exit_robust_list64(struct task_struct *curr) +static void exit_robust_list64(struct task_struct *curr, + struct robust_list_head __user *head) { pr_warn("32bit kernel should not allow ROBUST_LIST_64BIT"); } @@ -1250,9 +1251,9 @@ fetch_robust_entry32(u32 *uentry, struct robust_list __user **entry, * * We silently return on any sign of list-walking problem. */ -static void exit_robust_list32(struct task_struct *curr) +static void exit_robust_list32(struct task_struct *curr, + struct robust_list_head32 __user *head) { - struct robust_list_head32 __user *head = curr->compat_robust_list; struct robust_list __user *entry, *next_entry, *pending; unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; unsigned int next_pi; @@ -1318,6 +1319,70 @@ static void exit_robust_list32(struct task_struct *curr) } }
+long do_set_robust_list2(struct robust_list_head __user *head, + int index, unsigned int type) +{ + struct list_head *list2 = ¤t->robust_list2; + struct robust_list2_entry *prev, *new = NULL; + + if (index == -1) { + if (list_empty(list2)) { + index = 0; + } else { + prev = list_last_entry(list2, struct robust_list2_entry, list); + index = prev->index + 1; + } + + if (index >= ROBUST_LISTS_PER_TASK) + return -EINVAL; + + new = kmalloc(sizeof(struct robust_list2_entry), GFP_KERNEL); + if (!new) + return -ENOMEM; + + list_add_tail(&new->list, list2); + new->index = index; + + } else if (index >= 0) { + struct robust_list2_entry *curr; + + if (list_empty(list2)) + return -ENOENT; + + list_for_each_entry(curr, list2, list) { + if (index == curr->index) { + new = curr; + break; + } + } + + if (!new) + return -ENOENT; + } + + BUG_ON(!new); + new->head = head; + new->list_type = type; + + return index; +} + +struct robust_list_head __user *get_robust_list2(int index, struct task_struct *task) +{ + struct list_head *list2 = &task->robust_list2; + struct robust_list2_entry *curr; + + if (list_empty(list2) || index == -1) + return NULL; + + list_for_each_entry(curr, list2, list) { + if (index == curr->index) + return curr->head; + } + + return NULL; +} + #ifdef CONFIG_FUTEX_PI
/* @@ -1411,24 +1476,28 @@ static inline void exit_pi_state_list(struct task_struct *curr) { }
static void futex_cleanup(struct task_struct *tsk) { -#ifdef CONFIG_64BIT - if (unlikely(tsk->robust_list)) { - exit_robust_list64(tsk); - tsk->robust_list = NULL; - } -#else - if (unlikely(tsk->robust_list)) { - exit_robust_list32(tsk); - tsk->robust_list = NULL; - } -#endif + struct robust_list2_entry *curr, *n; + struct list_head *list2 = &tsk->robust_list2;
-#ifdef CONFIG_COMPAT - if (unlikely(tsk->compat_robust_list)) { - exit_robust_list32(tsk); - tsk->compat_robust_list = NULL; + /* + * Walk through the linked list, parsing robust lists and freeing the + * allocated lists + */ + if (unlikely(!list_empty(list2))) { + list_for_each_entry_safe(curr, n, list2, list) { + if (curr->head != NULL) { + if (curr->list_type == ROBUST_LIST_64BIT) + exit_robust_list64(tsk, curr->head); + else if (curr->list_type == ROBUST_LIST_32BIT) + exit_robust_list32(tsk, curr->head); + curr->head = NULL; + } + list_del_init(&curr->list); + kfree(curr); + } } -#endif + + tsk->robust_list_index = -1;
if (unlikely(!list_empty(&tsk->pi_state_list))) exit_pi_state_list(tsk); diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h index fcd1617212eed0e3c2367d2b463a0e019eda6d13..67201e51fa1798a21ff68f60b1e35977b9bd267b 100644 --- a/kernel/futex/futex.h +++ b/kernel/futex/futex.h @@ -467,6 +467,11 @@ extern int __futex_wait(u32 __user *uaddr, unsigned int flags, u32 val, extern int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val, ktime_t *abs_time, u32 bitset);
+extern long do_set_robust_list2(struct robust_list_head __user *head, + int index, unsigned int type); + +extern struct robust_list_head __user *get_robust_list2(int index, struct task_struct *task); + /** * struct futex_vector - Auxiliary struct for futex_waitv() * @w: Userspace provided data diff --git a/kernel/futex/syscalls.c b/kernel/futex/syscalls.c index dba193dfd216cc929c8f4d979aa2bcd99237e2d8..56ee1123cbd8ea26c8d22aa74e5faed2974ec577 100644 --- a/kernel/futex/syscalls.c +++ b/kernel/futex/syscalls.c @@ -20,6 +20,18 @@ * the list. There can only be one such pending lock. */
+#ifdef CONFIG_64BIT +static inline int robust_list_native_type(void) +{ + return ROBUST_LIST_64BIT; +} +#else +static inline int robust_list_native_type(void) +{ + return ROBUST_LIST_32BIT; +} +#endif + /** * sys_set_robust_list() - Set the robust-futex list head of a task * @head: pointer to the list-head @@ -28,17 +40,63 @@ SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head, size_t, len) { + unsigned int type = robust_list_native_type(); + int ret; + /* * The kernel knows only one size for now: */ if (unlikely(len != sizeof(*head))) return -EINVAL;
- current->robust_list = head; + ret = do_set_robust_list2(head, current->robust_list_index, type); + if (ret < 0) + return ret; + + current->robust_list_index = ret;
return 0; }
+#define ROBUST_LIST_FLAGS ROBUST_LIST_TYPE_MASK + +/* + * sys_set_robust_list2() + * + * When index == -1, create a new list for user. When index >= 0, try to find + * the corresponding list and re-set the head there. + * + * Return values: + * >= 0: success, index of the robust list + * -EINVAL: invalid flags, invalid index + * -ENOENT: requested index no where to be found + * -ENOMEM: error allocating new list + * -ESRCH: too many allocated lists + */ +SYSCALL_DEFINE3(set_robust_list2, struct robust_list_head __user *, head, + int, index, unsigned int, flags) +{ + unsigned int type; + + type = flags & ROBUST_LIST_TYPE_MASK; + + if (index < -1 || index >= ROBUST_LISTS_PER_TASK) + return -EINVAL; + + if ((flags & ~ROBUST_LIST_FLAGS) != 0) + return -EINVAL; + + if (((uintptr_t) head % sizeof(u32)) != 0) + return -EINVAL; + +#ifndef CONFIG_64BIT + if (type == ROBUST_LIST_64BIT) + return -EINVAL; +#endif + + return do_set_robust_list2(head, index, type); +} + /** * sys_get_robust_list() - Get the robust-futex list head of a task * @pid: pid of the process [zero for current task] @@ -52,6 +110,7 @@ SYSCALL_DEFINE3(get_robust_list, int, pid, struct robust_list_head __user *head; unsigned long ret; struct task_struct *p; + int index;
rcu_read_lock();
@@ -68,9 +127,11 @@ SYSCALL_DEFINE3(get_robust_list, int, pid, if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS)) goto err_unlock;
- head = p->robust_list; + index = p->robust_list_index; rcu_read_unlock();
+ head = get_robust_list2(index, p); + if (put_user(sizeof(*head), len_ptr)) return -EFAULT; return put_user(head, head_ptr); @@ -443,10 +504,19 @@ COMPAT_SYSCALL_DEFINE2(set_robust_list, struct robust_list_head32 __user *, head, compat_size_t, len) { + unsigned int type = ROBUST_LIST_32BIT; + int ret; + if (unlikely(len != sizeof(*head))) return -EINVAL;
- current->compat_robust_list = head; + ret = do_set_robust_list2((struct robust_list_head __user *) head, + current->robust_list_index, type); + if (ret < 0) + return ret; + + current->robust_list_index = ret; +
return 0; } @@ -458,6 +528,7 @@ COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid, struct robust_list_head32 __user *head; unsigned long ret; struct task_struct *p; + int index;
rcu_read_lock();
@@ -474,9 +545,11 @@ COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid, if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS)) goto err_unlock;
- head = p->compat_robust_list; + index = p->compat_robust_list_index; rcu_read_unlock();
+ head = (struct robust_list_head32 __user *) get_robust_list2(index, p); + if (put_user(sizeof(*head), len_ptr)) return -EFAULT; return put_user(ptr_to_compat(head), head_ptr);
Hi André,
kernel test robot noticed the following build errors:
[auto build test ERROR on 3ee84e3dd88e39b55b534e17a7b9a181f1d46809]
url: https://github.com/intel-lab-lkp/linux/commits/Andr-Almeida/selftests-futex-... base: 3ee84e3dd88e39b55b534e17a7b9a181f1d46809 patch link: https://lore.kernel.org/r/20250520-tonyk-robust_futex-v4-4-1123093e59de%40ig... patch subject: [PATCH v4 4/7] futex: Create set_robust_list2 config: i386-buildonly-randconfig-003-20250521 (https://download.01.org/0day-ci/archive/20250521/202505212200.ditHHp5E-lkp@i...) compiler: gcc-12 (Debian 12.2.0-14) 12.2.0 reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250521/202505212200.ditHHp5E-lkp@i...)
If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot lkp@intel.com | Closes: https://lore.kernel.org/oe-kbuild-all/202505212200.ditHHp5E-lkp@intel.com/
All errors (new ones prefixed by >>):
In file included from <command-line>:
./usr/include/linux/futex.h:177:26: error: field 'list' has incomplete type
177 | struct list_head list; | ^~~~
Wire up the new set_robust_list2 syscall in all available architectures.
Signed-off-by: André Almeida andrealmeid@igalia.com --- arch/alpha/kernel/syscalls/syscall.tbl | 1 + arch/arm/tools/syscall.tbl | 1 + arch/m68k/kernel/syscalls/syscall.tbl | 1 + arch/microblaze/kernel/syscalls/syscall.tbl | 1 + arch/mips/kernel/syscalls/syscall_n32.tbl | 1 + arch/mips/kernel/syscalls/syscall_n64.tbl | 1 + arch/mips/kernel/syscalls/syscall_o32.tbl | 1 + arch/parisc/kernel/syscalls/syscall.tbl | 1 + arch/powerpc/kernel/syscalls/syscall.tbl | 1 + arch/s390/kernel/syscalls/syscall.tbl | 1 + arch/sh/kernel/syscalls/syscall.tbl | 1 + arch/sparc/kernel/syscalls/syscall.tbl | 1 + arch/x86/entry/syscalls/syscall_32.tbl | 1 + arch/x86/entry/syscalls/syscall_64.tbl | 1 + arch/xtensa/kernel/syscalls/syscall.tbl | 1 + kernel/sys_ni.c | 1 + scripts/syscall.tbl | 1 + 17 files changed, 17 insertions(+)
diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl index 2dd6340de6b4efddc406f0c235701c15cf02f650..aecc167ac7706d25da73db8099f0813e268b820c 100644 --- a/arch/alpha/kernel/syscalls/syscall.tbl +++ b/arch/alpha/kernel/syscalls/syscall.tbl @@ -507,3 +507,4 @@ 575 common listxattrat sys_listxattrat 576 common removexattrat sys_removexattrat 577 common open_tree_attr sys_open_tree_attr +578 common set_robust_list2 sys_robust_list2 diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl index 27c1d5ebcd91c8c296dc6676307f66bfdf4ab78d..2e47ae5dc9a426d8e5e9dacf29caa54223cf2f5a 100644 --- a/arch/arm/tools/syscall.tbl +++ b/arch/arm/tools/syscall.tbl @@ -482,3 +482,4 @@ 465 common listxattrat sys_listxattrat 466 common removexattrat sys_removexattrat 467 common open_tree_attr sys_open_tree_attr +468 common set_robust_list2 sys_set_robust_list2 diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl index 9fe47112c586f152662af38a9a7f90957cb96cf8..7bcc8cc628c80a44fea2b53d5c69ab5e5f10a1d2 100644 --- a/arch/m68k/kernel/syscalls/syscall.tbl +++ b/arch/m68k/kernel/syscalls/syscall.tbl @@ -467,3 +467,4 @@ 465 common listxattrat sys_listxattrat 466 common removexattrat sys_removexattrat 467 common open_tree_attr sys_open_tree_attr +468 common set_robust_list2 sys_set_robust_list2 diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl index 7b6e97828e552d4da90046ddfcd4a55723e522bb..cd23608afe7e7dadfbf8e21df0486b85bfcb99ce 100644 --- a/arch/microblaze/kernel/syscalls/syscall.tbl +++ b/arch/microblaze/kernel/syscalls/syscall.tbl @@ -473,3 +473,4 @@ 465 common listxattrat sys_listxattrat 466 common removexattrat sys_removexattrat 467 common open_tree_attr sys_open_tree_attr +468 common set_robust_list2 sys_set_robust_list2 diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl index aa70e371bb54ab5d9c8dd8923b6ecf9693ee914d..0a31452ef6ed8fee8f1e2ead5d44acfbbe275fe9 100644 --- a/arch/mips/kernel/syscalls/syscall_n32.tbl +++ b/arch/mips/kernel/syscalls/syscall_n32.tbl @@ -406,3 +406,4 @@ 465 n32 listxattrat sys_listxattrat 466 n32 removexattrat sys_removexattrat 467 n32 open_tree_attr sys_open_tree_attr +468 n32 set_robust_list2 sys_set_robust_list2 diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl index 1e8c44c7b61492eabf00c777831e457a7a6e579c..4cb5a72256338f6fb407f940f1883d523113d609 100644 --- a/arch/mips/kernel/syscalls/syscall_n64.tbl +++ b/arch/mips/kernel/syscalls/syscall_n64.tbl @@ -382,3 +382,4 @@ 465 n64 listxattrat sys_listxattrat 466 n64 removexattrat sys_removexattrat 467 n64 open_tree_attr sys_open_tree_attr +468 n64 set_robust_list2 sys_set_robust_list2 diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl index 114a5a1a62302e32dd74d1679ff423a2d57c3c6b..c46238e9edd00d2861edcfa87c5ce7a62bfdc3d4 100644 --- a/arch/mips/kernel/syscalls/syscall_o32.tbl +++ b/arch/mips/kernel/syscalls/syscall_o32.tbl @@ -455,3 +455,4 @@ 465 o32 listxattrat sys_listxattrat 466 o32 removexattrat sys_removexattrat 467 o32 open_tree_attr sys_open_tree_attr +468 o32 set_robust_list2 sys_set_robust_list2 diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl index 94df3cb957e9d547d192e8732c0cf23ef2b5ce5d..71071489a18375013bbfbe26578a634283c1e07b 100644 --- a/arch/parisc/kernel/syscalls/syscall.tbl +++ b/arch/parisc/kernel/syscalls/syscall.tbl @@ -466,3 +466,4 @@ 465 common listxattrat sys_listxattrat 466 common removexattrat sys_removexattrat 467 common open_tree_attr sys_open_tree_attr +468 common set_robust_list2 sys_set_robust_list2 diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl index 9a084bdb892694bc562f514b55212d167cbac12f..edc4d0bef3f1c7ab826ea8180e7f5ceba4774c07 100644 --- a/arch/powerpc/kernel/syscalls/syscall.tbl +++ b/arch/powerpc/kernel/syscalls/syscall.tbl @@ -558,3 +558,4 @@ 465 common listxattrat sys_listxattrat 466 common removexattrat sys_removexattrat 467 common open_tree_attr sys_open_tree_attr +468 common set_robust_list2 sys_set_robust_list2 diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl index a4569b96ef06c54ce7aa795d039541c90a38284f..ff8c594073ec8c3486cc61544d14a338d3f3a906 100644 --- a/arch/s390/kernel/syscalls/syscall.tbl +++ b/arch/s390/kernel/syscalls/syscall.tbl @@ -470,3 +470,4 @@ 465 common listxattrat sys_listxattrat sys_listxattrat 466 common removexattrat sys_removexattrat sys_removexattrat 467 common open_tree_attr sys_open_tree_attr sys_open_tree_attr +468 common set_robust_list2 sys_set_robust_list2 sys_set_robust_list2 diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl index 52a7652fcff6394b96ace1f3b0ed72250ee5e669..507789194570a9e7b492b210be30bb41021be289 100644 --- a/arch/sh/kernel/syscalls/syscall.tbl +++ b/arch/sh/kernel/syscalls/syscall.tbl @@ -471,3 +471,4 @@ 465 common listxattrat sys_listxattrat 466 common removexattrat sys_removexattrat 467 common open_tree_attr sys_open_tree_attr +468 common set_robust_list2 sys_set_robust_list2 diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl index 83e45eb6c095a36baaf749927628e6052fe900e6..8d1122c2235b8d5082a11392e68787efe55f58be 100644 --- a/arch/sparc/kernel/syscalls/syscall.tbl +++ b/arch/sparc/kernel/syscalls/syscall.tbl @@ -513,3 +513,4 @@ 465 common listxattrat sys_listxattrat 466 common removexattrat sys_removexattrat 467 common open_tree_attr sys_open_tree_attr +468 common set_robust_list2 sys_set_robust_list2 diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl index ac007ea00979dc28b0ef7c002a0615ce86dd3101..cbc0c469e66ecf7b8a61e82c38b07ecc63f6fe23 100644 --- a/arch/x86/entry/syscalls/syscall_32.tbl +++ b/arch/x86/entry/syscalls/syscall_32.tbl @@ -473,3 +473,4 @@ 465 i386 listxattrat sys_listxattrat 466 i386 removexattrat sys_removexattrat 467 i386 open_tree_attr sys_open_tree_attr +468 i386 set_robust_list2 sys_set_robust_list2 diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl index cfb5ca41e30de1a4e073750096f5b51a2ec137d2..b420217c72fc50ad90f291812972019606c5ff69 100644 --- a/arch/x86/entry/syscalls/syscall_64.tbl +++ b/arch/x86/entry/syscalls/syscall_64.tbl @@ -391,6 +391,7 @@ 465 common listxattrat sys_listxattrat 466 common removexattrat sys_removexattrat 467 common open_tree_attr sys_open_tree_attr +468 common set_robust_list2 sys_set_robust_list2
# # Due to a historical design error, certain syscalls are numbered differently diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl b/arch/xtensa/kernel/syscalls/syscall.tbl index f657a77314f8667fa019a01e10c84ea270024adc..6b852ee8a1621c7dd24f6cd37fd990f5ff8d8527 100644 --- a/arch/xtensa/kernel/syscalls/syscall.tbl +++ b/arch/xtensa/kernel/syscalls/syscall.tbl @@ -438,3 +438,4 @@ 465 common listxattrat sys_listxattrat 466 common removexattrat sys_removexattrat 467 common open_tree_attr sys_open_tree_attr +468 common set_robust_list2 sys_set_robust_list2 diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c index c00a86931f8c6cb30d35a9d56cbcc5994add90e1..71fbac6176c8886f4fa8dd437b0aedd5f14e9f74 100644 --- a/kernel/sys_ni.c +++ b/kernel/sys_ni.c @@ -195,6 +195,7 @@ COND_SYSCALL(move_pages); COND_SYSCALL(set_mempolicy_home_node); COND_SYSCALL(cachestat); COND_SYSCALL(mseal); +COND_SYSCALL(set_robust_list2);
COND_SYSCALL(perf_event_open); COND_SYSCALL(accept4); diff --git a/scripts/syscall.tbl b/scripts/syscall.tbl index 580b4e246aecd5f07d542943ba68fc4ed5961660..07d7e776d0329659e70a9a55ffff7ac18eb3ff87 100644 --- a/scripts/syscall.tbl +++ b/scripts/syscall.tbl @@ -408,3 +408,4 @@ 465 common listxattrat sys_listxattrat 466 common removexattrat sys_removexattrat 467 common open_tree_attr sys_open_tree_attr +468 common set_robust_list2 sys_set_robust_list2
Hi André,
kernel test robot noticed the following build errors:
[auto build test ERROR on 3ee84e3dd88e39b55b534e17a7b9a181f1d46809]
url: https://github.com/intel-lab-lkp/linux/commits/Andr-Almeida/selftests-futex-... base: 3ee84e3dd88e39b55b534e17a7b9a181f1d46809 patch link: https://lore.kernel.org/r/20250520-tonyk-robust_futex-v4-5-1123093e59de%40ig... patch subject: [PATCH v4 5/7] futex: Wire up set_robust_list2 syscall config: arc-randconfig-001-20250521 (https://download.01.org/0day-ci/archive/20250522/202505220350.ZektmdF0-lkp@i...) compiler: arc-linux-gcc (GCC) 10.5.0 reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250522/202505220350.ZektmdF0-lkp@i...)
If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot lkp@intel.com | Closes: https://lore.kernel.org/oe-kbuild-all/202505220350.ZektmdF0-lkp@intel.com/
All errors (new ones prefixed by >>):
| ^ ./arch/arc/include/generated/asm/syscall_table_32.h:460:1: note: in expansion of macro '__SYSCALL' 460 | __SYSCALL(459, sys_lsm_get_self_attr) | ^~~~~~~~~ arch/arc/kernel/sys.c:13:36: warning: initialized field overwritten [-Woverride-init] 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^ ./arch/arc/include/generated/asm/syscall_table_32.h:461:1: note: in expansion of macro '__SYSCALL' 461 | __SYSCALL(460, sys_lsm_set_self_attr) | ^~~~~~~~~ arch/arc/kernel/sys.c:13:36: note: (near initialization for 'sys_call_table[460]') 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^ ./arch/arc/include/generated/asm/syscall_table_32.h:461:1: note: in expansion of macro '__SYSCALL' 461 | __SYSCALL(460, sys_lsm_set_self_attr) | ^~~~~~~~~ arch/arc/kernel/sys.c:13:36: warning: initialized field overwritten [-Woverride-init] 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^ ./arch/arc/include/generated/asm/syscall_table_32.h:462:1: note: in expansion of macro '__SYSCALL' 462 | __SYSCALL(461, sys_lsm_list_modules) | ^~~~~~~~~ arch/arc/kernel/sys.c:13:36: note: (near initialization for 'sys_call_table[461]') 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^ ./arch/arc/include/generated/asm/syscall_table_32.h:462:1: note: in expansion of macro '__SYSCALL' 462 | __SYSCALL(461, sys_lsm_list_modules) | ^~~~~~~~~ arch/arc/kernel/sys.c:13:36: warning: initialized field overwritten [-Woverride-init] 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^ ./arch/arc/include/generated/asm/syscall_table_32.h:463:1: note: in expansion of macro '__SYSCALL' 463 | __SYSCALL(462, sys_mseal) | ^~~~~~~~~ arch/arc/kernel/sys.c:13:36: note: (near initialization for 'sys_call_table[462]') 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^ ./arch/arc/include/generated/asm/syscall_table_32.h:463:1: note: in expansion of macro '__SYSCALL' 463 | __SYSCALL(462, sys_mseal) | ^~~~~~~~~ arch/arc/kernel/sys.c:13:36: warning: initialized field overwritten [-Woverride-init] 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^ ./arch/arc/include/generated/asm/syscall_table_32.h:464:1: note: in expansion of macro '__SYSCALL' 464 | __SYSCALL(463, sys_setxattrat) | ^~~~~~~~~ arch/arc/kernel/sys.c:13:36: note: (near initialization for 'sys_call_table[463]') 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^ ./arch/arc/include/generated/asm/syscall_table_32.h:464:1: note: in expansion of macro '__SYSCALL' 464 | __SYSCALL(463, sys_setxattrat) | ^~~~~~~~~ arch/arc/kernel/sys.c:13:36: warning: initialized field overwritten [-Woverride-init] 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^ ./arch/arc/include/generated/asm/syscall_table_32.h:465:1: note: in expansion of macro '__SYSCALL' 465 | __SYSCALL(464, sys_getxattrat) | ^~~~~~~~~ arch/arc/kernel/sys.c:13:36: note: (near initialization for 'sys_call_table[464]') 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^ ./arch/arc/include/generated/asm/syscall_table_32.h:465:1: note: in expansion of macro '__SYSCALL' 465 | __SYSCALL(464, sys_getxattrat) | ^~~~~~~~~ arch/arc/kernel/sys.c:13:36: warning: initialized field overwritten [-Woverride-init] 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^ ./arch/arc/include/generated/asm/syscall_table_32.h:466:1: note: in expansion of macro '__SYSCALL' 466 | __SYSCALL(465, sys_listxattrat) | ^~~~~~~~~ arch/arc/kernel/sys.c:13:36: note: (near initialization for 'sys_call_table[465]') 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^ ./arch/arc/include/generated/asm/syscall_table_32.h:466:1: note: in expansion of macro '__SYSCALL' 466 | __SYSCALL(465, sys_listxattrat) | ^~~~~~~~~ arch/arc/kernel/sys.c:13:36: warning: initialized field overwritten [-Woverride-init] 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^ ./arch/arc/include/generated/asm/syscall_table_32.h:467:1: note: in expansion of macro '__SYSCALL' 467 | __SYSCALL(466, sys_removexattrat) | ^~~~~~~~~ arch/arc/kernel/sys.c:13:36: note: (near initialization for 'sys_call_table[466]') 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^ ./arch/arc/include/generated/asm/syscall_table_32.h:467:1: note: in expansion of macro '__SYSCALL' 467 | __SYSCALL(466, sys_removexattrat) | ^~~~~~~~~ arch/arc/kernel/sys.c:13:36: warning: initialized field overwritten [-Woverride-init] 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^ ./arch/arc/include/generated/asm/syscall_table_32.h:468:1: note: in expansion of macro '__SYSCALL' 468 | __SYSCALL(467, sys_open_tree_attr) | ^~~~~~~~~ arch/arc/kernel/sys.c:13:36: note: (near initialization for 'sys_call_table[467]') 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^ ./arch/arc/include/generated/asm/syscall_table_32.h:468:1: note: in expansion of macro '__SYSCALL' 468 | __SYSCALL(467, sys_open_tree_attr) | ^~~~~~~~~
./arch/arc/include/generated/asm/syscall_table_32.h:469:16: error: 'sys_set_robust_list2' undeclared here (not in a function); did you mean 'sys_set_robust_list'?
469 | __SYSCALL(468, sys_set_robust_list2) | ^~~~~~~~~~~~~~~~~~~~ arch/arc/kernel/sys.c:13:37: note: in definition of macro '__SYSCALL' 13 | #define __SYSCALL(nr, call) [nr] = (call), | ^~~~
Remove the limit of ROBUST_LIST_LIMIT elements that a robust list can have, for the ones created with the new interface. This is done by overwritten the list as it's proceeded in a way that we avoid circular lists.
For the old interface, we keep the limited behavior to avoid changing the API.
Signed-off-by: André Almeida andrealmeid@igalia.com --- kernel/futex/core.c | 50 ++++++++++++++++++++++++++++++++++++-------------- 1 file changed, 36 insertions(+), 14 deletions(-)
diff --git a/kernel/futex/core.c b/kernel/futex/core.c index 49b3bc592948a811f995017027f33ad8f285531f..61f0b48a2bcd8ab926754980ab3454b9ec13a344 100644 --- a/kernel/futex/core.c +++ b/kernel/futex/core.c @@ -1152,7 +1152,8 @@ static inline int fetch_robust_entry(struct robust_list __user **entry, * We silently return on any sign of list-walking problem. */ static void exit_robust_list64(struct task_struct *curr, - struct robust_list_head __user *head) + struct robust_list_head __user *head, + bool destroyable) { struct robust_list __user *entry, *next_entry, *pending; unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; @@ -1196,13 +1197,17 @@ static void exit_robust_list64(struct task_struct *curr, } if (rc) return; - entry = next_entry; - pi = next_pi; + /* * Avoid excessively long or circular lists: */ - if (!--limit) + if (!destroyable && !--limit) break; + else + put_user(&head->list, &entry->next); + + entry = next_entry; + pi = next_pi;
cond_resched(); } @@ -1214,7 +1219,8 @@ static void exit_robust_list64(struct task_struct *curr, } #else static void exit_robust_list64(struct task_struct *curr, - struct robust_list_head __user *head) + struct robust_list_head __user *head, + bool destroyable) { pr_warn("32bit kernel should not allow ROBUST_LIST_64BIT"); } @@ -1252,7 +1258,8 @@ fetch_robust_entry32(u32 *uentry, struct robust_list __user **entry, * We silently return on any sign of list-walking problem. */ static void exit_robust_list32(struct task_struct *curr, - struct robust_list_head32 __user *head) + struct robust_list_head32 __user *head, + bool destroyable) { struct robust_list __user *entry, *next_entry, *pending; unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; @@ -1301,14 +1308,17 @@ static void exit_robust_list32(struct task_struct *curr, } if (rc) return; - uentry = next_uentry; - entry = next_entry; - pi = next_pi; /* * Avoid excessively long or circular lists: */ - if (!--limit) + if (!destroyable && !--limit) break; + else + put_user((struct robust_list __user *) &head->list, &entry->next); + + uentry = next_uentry; + entry = next_entry; + pi = next_pi;
cond_resched(); } @@ -1474,26 +1484,38 @@ static void exit_pi_state_list(struct task_struct *curr) static inline void exit_pi_state_list(struct task_struct *curr) { } #endif
+/* + * futex_cleanup - After the task exists, process the robust lists + * + * Walk through the linked list, parsing robust lists and freeing the + * allocated lists. Lists created with the set_robust_list2 don't have a limit + * for sizing and can be destroyed while we walk on it to avoid circular list. + */ static void futex_cleanup(struct task_struct *tsk) { struct robust_list2_entry *curr, *n; struct list_head *list2 = &tsk->robust_list2; + bool destroyable = true; + int i = 0;
/* - * Walk through the linked list, parsing robust lists and freeing the - * allocated lists */ if (unlikely(!list_empty(list2))) { list_for_each_entry_safe(curr, n, list2, list) { + destroyable = true; + if (tsk->robust_list_index == i) + destroyable = false; + if (curr->head != NULL) { if (curr->list_type == ROBUST_LIST_64BIT) - exit_robust_list64(tsk, curr->head); + exit_robust_list64(tsk, curr->head, destroyable); else if (curr->list_type == ROBUST_LIST_32BIT) - exit_robust_list32(tsk, curr->head); + exit_robust_list32(tsk, curr->head, destroyable); curr->head = NULL; } list_del_init(&curr->list); kfree(curr); + i++; } }
Expand the current robust list test for the new set_robust_list2 syscall. Create an option to make it possible to run the same tests using the new syscall, and also add two new relevant test: test long lists (bigger than ROBUST_LIST_LIMIT) and for unaligned addresses.
Signed-off-by: André Almeida andrealmeid@igalia.com --- .../selftests/futex/functional/robust_list.c | 160 ++++++++++++++++++++- 1 file changed, 156 insertions(+), 4 deletions(-)
diff --git a/tools/testing/selftests/futex/functional/robust_list.c b/tools/testing/selftests/futex/functional/robust_list.c index 42690b2440fd29a9b12c46f67f9645ccc93d1147..004ad79ff6171c411fd47e699e3c38889544218e 100644 --- a/tools/testing/selftests/futex/functional/robust_list.c +++ b/tools/testing/selftests/futex/functional/robust_list.c @@ -35,16 +35,45 @@ #include <stddef.h> #include <sys/mman.h> #include <sys/wait.h> +#include <stdint.h>
#define STACK_SIZE (1024 * 1024)
#define FUTEX_TIMEOUT 3
+#define SYS_set_robust_list2 468 + +enum robust_list2_type { + ROBUST_LIST_32BIT, + ROBUST_LIST_64BIT, +}; + static pthread_barrier_t barrier, barrier2;
+bool robust2 = false; + int set_robust_list(struct robust_list_head *head, size_t len) { - return syscall(SYS_set_robust_list, head, len); + int ret, flags; + + if (!robust2) { + return syscall(SYS_set_robust_list, head, len); + } + + if (sizeof(head) == 8) + flags = ROBUST_LIST_64BIT; + else + flags = ROBUST_LIST_32BIT; + + /* + * We act as we have just one list here. We try to use the first slot, + * but if it hasn't been alocated yet we allocate it. + */ + ret = syscall(SYS_set_robust_list2, head, 0, flags); + if (ret == -1 && errno == ENOENT) + ret = syscall(SYS_set_robust_list2, head, -1, flags); + + return ret; }
int get_robust_list(int pid, struct robust_list_head **head, size_t *len_ptr) @@ -246,6 +275,11 @@ static void test_set_robust_list_invalid_size(void) size_t head_size = sizeof(struct robust_list_head); int ret;
+ if (robust2) { + ksft_test_result_skip("This test is only for old robust interface\n"); + return; + } + ret = set_robust_list(&head, head_size); ASSERT_EQ(ret, 0);
@@ -321,6 +355,11 @@ static void test_get_robust_list_child(void) struct robust_list_head head, *get_head; size_t len_ptr;
+ if (robust2) { + ksft_test_result_skip("Not implemented in the new robust interface\n"); + return; + } + ret = pthread_barrier_init(&barrier, NULL, 2); ret = pthread_barrier_init(&barrier2, NULL, 2); ASSERT_EQ(ret, 0); @@ -332,7 +371,7 @@ static void test_get_robust_list_child(void)
ret = get_robust_list(tid, &get_head, &len_ptr); ASSERT_EQ(ret, 0); - ASSERT_EQ(&head, get_head); + ASSERT_EQ(get_head, &head);
pthread_barrier_wait(&barrier2);
@@ -507,11 +546,119 @@ static void test_circular_list(void) ksft_test_result_pass("%s\n", __func__); }
+#define ROBUST_LIST_LIMIT 2048 +#define CHILD_LIST_LIMIT (ROBUST_LIST_LIMIT + 10) + +static int child_robust_list_limit(void *arg) +{ + struct lock_struct *locks; + struct robust_list *list; + struct robust_list_head head; + int ret, i; + + locks = (struct lock_struct *) arg; + + ret = set_list(&head); + if (ret) + ksft_test_result_fail("set_list error\n"); + + /* + * Create a very long list of locks + */ + head.list.next = &locks[0].list; + + list = head.list.next; + for (i = 0; i < CHILD_LIST_LIMIT - 1; i++) { + list->next = &locks[i+1].list; + list = list->next; + } + list->next = &head.list; + + /* + * Grab the lock in the last one, and die without releasing it + */ + mutex_lock(&locks[CHILD_LIST_LIMIT], &head, false); + pthread_barrier_wait(&barrier); + + sleep(1); + + return 0; +} + +/* + * The old robust list used to have a limit of 2048 items from the kernel side. + * After this limit the kernel stops walking the list and ignore the other + * futexes, causing deadlocks. + * + * For the new interface, test if we can wait for a list of more than 2048 + * elements. + */ +static void test_robust_list_limit(void) +{ + struct lock_struct locks[CHILD_LIST_LIMIT + 1]; + _Atomic(unsigned int) *futex = &locks[CHILD_LIST_LIMIT].futex; + struct robust_list_head head; + int ret; + + if (!robust2) { + ksft_test_result_skip("This test is only for new robust interface\n"); + return; + } + + *futex = 0; + + ret = set_list(&head); + ASSERT_EQ(ret, 0); + + ret = pthread_barrier_init(&barrier, NULL, 2); + ASSERT_EQ(ret, 0); + + create_child(child_robust_list_limit, locks); + + /* + * After the child thread creates the very long list of locks, wait on + * the last one. + */ + pthread_barrier_wait(&barrier); + ret = mutex_lock(&locks[CHILD_LIST_LIMIT], &head, false); + + if (ret != 0) + printf("futex wait returned %d\n", errno); + ASSERT_EQ(ret, 0); + + ASSERT_TRUE(*futex | FUTEX_OWNER_DIED); + + wait(NULL); + pthread_barrier_destroy(&barrier); + + ksft_test_result_pass("%s\n", __func__); +} + +/* + * The kernel should refuse an unaligned head pointer + */ +static void test_unaligned_address(void) +{ + struct robust_list_head head, *h; + int ret; + + if (!robust2) { + ksft_test_result_skip("This test is only for new robust interface\n"); + return; + } + + h = (struct robust_list_head *) ((uintptr_t) &head + 1); + ret = set_list(h); + ASSERT_EQ(ret, -1); + ASSERT_EQ(errno, EINVAL); +} + void usage(char *prog) { printf("Usage: %s\n", prog); printf(" -c Use color\n"); printf(" -h Display this help message\n"); + printf(" -n Use robust2 syscall\n"); printf(" -v L Verbosity level: %d=QUIET %d=CRITICAL %d=INFO\n", VQUIET, VCRITICAL, VINFO); } @@ -520,7 +667,7 @@ int main(int argc, char *argv[]) { int c;
- while ((c = getopt(argc, argv, "cht:v:")) != -1) { + while ((c = getopt(argc, argv, "chnt:v:")) != -1) { switch (c) { case 'c': log_color(1); @@ -531,6 +678,9 @@ int main(int argc, char *argv[]) case 'v': log_verbosity(atoi(optarg)); break; + case 'n': + robust2 = true; + break; default: usage(basename(argv[0])); exit(1); @@ -538,7 +688,7 @@ int main(int argc, char *argv[]) }
ksft_print_header(); - ksft_set_plan(7); + ksft_set_plan(8);
test_robustness();
@@ -548,6 +698,8 @@ int main(int argc, char *argv[]) test_set_list_op_pending(); test_robust_list_multiple_elements(); test_circular_list(); + test_robust_list_limit(); + test_unaligned_address();
ksft_print_cnts(); return 0;
linux-kselftest-mirror@lists.linaro.org
-
André Almeida -
kernel test robot