-----Original Message----- From: Eric W. Biederman ebiederm@xmission.com Sent: Tuesday, August 24, 2021 5:07 AM To: Alexey Gladkov legion@kernel.org Cc: Ma, XinjianX xinjianx.ma@intel.com; linux-kselftest@vger.kernel.org; lkp lkp@intel.com; akpm@linux-foundation.org; axboe@kernel.dk; christian.brauner@ubuntu.com; containers@lists.linux-foundation.org; jannh@google.com; keescook@chromium.org; kernel- hardening@lists.openwall.com; linux-kernel@vger.kernel.org; linux- mm@kvack.org; oleg@redhat.com; torvalds@linux-foundation.org Subject: [PATCH] ucounts: Fix regression preventing increasing of rlimits in init_user_ns
"Ma, XinjianX" xinjianx.ma@intel.com reported:
When lkp team run kernel selftests, we found after these series of patches, testcase mqueue: mq_perf_tests in kselftest failed with following
message.
# selftests: mqueue: mq_perf_tests # # Initial system state: # Using queue path: /mq_perf_tests # RLIMIT_MSGQUEUE(soft): 819200 # RLIMIT_MSGQUEUE(hard): 819200 # Maximum Message Size: 8192 # Maximum Queue Size: 10 # Nice value: 0 # # Adjusted system state for testing: # RLIMIT_MSGQUEUE(soft): (unlimited) # RLIMIT_MSGQUEUE(hard): (unlimited) # Maximum Message Size: 16777216 # Maximum Queue Size: 65530 # Nice value: -20 # Continuous mode: (disabled) # CPUs to pin: 3 # ./mq_perf_tests: mq_open() at 296: Too many open files not ok 2 selftests: mqueue: mq_perf_tests # exit=1 ```
Test env: rootfs: debian-10 gcc version: 9
After investigation the problem turned out to be that ucount_max for the rlimits in init_user_ns was being set to the initial rlimit value. The practical problem is that ucount_max provides a limit that applications inside the user namespace can not exceed. Which means in practice that rlimits that have been converted to use the ucount infrastructure were not able to exceend their initial rlimits.
Solve this by setting the relevant values of ucount_max to RLIM_INIFINITY. A limit in init_user_ns is pointless so the code should allow the values to grow as large as possible without riscking an underflow or an overflow.
As the ltp test case was a bit of a pain I have reproduced the rlimit failure and tested the fix with the following little C program:
#include <stdio.h> #include <fcntl.h> #include <sys/stat.h> #include <mqueue.h> #include <sys/time.h> #include <sys/resource.h> #include <errno.h> #include <string.h> #include <stdlib.h> #include <limits.h> #include <unistd.h>
int main(int argc, char **argv) { struct mq_attr mq_attr; struct rlimit rlim; mqd_t mqd; int ret;
ret = getrlimit(RLIMIT_MSGQUEUE, &rlim); if (ret != 0) { fprintf(stderr, "getrlimit(RLIMIT_MSGQUEUE) failed: %s\n",
strerror(errno));
exit(EXIT_FAILURE);} printf("RLIMIT_MSGQUEUE %lu %lu\n", rlim.rlim_cur, rlim.rlim_max); rlim.rlim_cur = RLIM_INFINITY; rlim.rlim_max = RLIM_INFINITY; ret = setrlimit(RLIMIT_MSGQUEUE, &rlim); if (ret != 0) { fprintf(stderr, "setrlimit(RLIMIT_MSGQUEUE, RLIM_INFINITY)
failed: %s\n", strerror(errno));
exit(EXIT_FAILURE);}
memset(&mq_attr, 0, sizeof(struct mq_attr)); mq_attr.mq_maxmsg = 65536 - 1; mq_attr.mq_msgsize = 16*1024*1024 - 1;
mqd = mq_open("/mq_rlimit_test", O_RDONLY|O_CREAT, 0600,
&mq_attr);
if (mqd == (mqd_t)-1) { fprintf(stderr, "mq_open failed: %s\n", strerror(errno)); exit(EXIT_FAILURE); } ret = mq_close(mqd); if (ret) { fprintf(stderr, "mq_close failed; %s\n", strerror(errno)); exit(EXIT_FAILURE); }
return EXIT_SUCCESS; }
Fixes: 6e52a9f0532f ("Reimplement RLIMIT_MSGQUEUE on top of ucounts") Fixes: d7c9e99aee48 ("Reimplement RLIMIT_MEMLOCK on top of ucounts") Fixes: d64696905554 ("Reimplement RLIMIT_SIGPENDING on top of ucounts") Fixes: 21d1c5e386bc ("Reimplement RLIMIT_NPROC on top of ucounts") Reported-by: kernel test robot lkp@intel.com
Sorry, but <> around email address is needed Reported-by: kernel test robot lkp@intel.com
Acked-by: Alexey Gladkov legion@kernel.org Signed-off-by: "Eric W. Biederman" ebiederm@xmission.com
This is a simplified version of my previous change that I have tested and will push out to linux-next and then to Linus shortly.
kernel/fork.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/fork.c b/kernel/fork.c index bc94b2cc5995..44f4c2d83763 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -828,10 +828,10 @@ void __init fork_init(void) for (i = 0; i < MAX_PER_NAMESPACE_UCOUNTS; i++) init_user_ns.ucount_max[i] = max_threads/2;
- set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC,
task_rlimit(&init_task, RLIMIT_NPROC));
- set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE,
task_rlimit(&init_task, RLIMIT_MSGQUEUE));
- set_rlimit_ucount_max(&init_user_ns,
UCOUNT_RLIMIT_SIGPENDING, task_rlimit(&init_task, RLIMIT_SIGPENDING));
- set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK,
task_rlimit(&init_task, RLIMIT_MEMLOCK));
- set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC,
RLIM_INFINITY);
- set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE,
RLIM_INFINITY);
- set_rlimit_ucount_max(&init_user_ns,
UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY);
- set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK,
RLIM_INFINITY);
#ifdef CONFIG_VMAP_STACK cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache", -- 2.20.1