Hi,
Here is a small set of rseq fixes aiming Linux 5.4. Those should be backported to stable kernels >= 4.18.
Thanks,
Mathieu
Mathieu Desnoyers (3): rseq: Fix: Reject unknown flags on rseq unregister rseq: Fix: Unregister rseq for clone CLONE_VM rseq/selftests: Fix: Namespace gettid() for compatibility with glibc 2.30
include/linux/sched.h | 4 ++-- kernel/rseq.c | 2 ++ tools/testing/selftests/rseq/param_test.c | 18 ++++++++++-------- 3 files changed, 14 insertions(+), 10 deletions(-)
It is preferrable to reject unknown flags within rseq unregistration rather than to ignore them. It is an oversight caused by the fact that the check for unknown flags is after the rseq unregister flag check.
Signed-off-by: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Peter Zijlstra (Intel) peterz@infradead.org Cc: "Paul E. McKenney" paulmck@linux.ibm.com Cc: Boqun Feng boqun.feng@gmail.com Cc: "H . Peter Anvin" hpa@zytor.com Cc: Paul Turner pjt@google.com Cc: linux-api@vger.kernel.org Cc: stable@vger.kernel.org # v4.18+ --- kernel/rseq.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/kernel/rseq.c b/kernel/rseq.c index 27c48eb7de40..a4f86a9d6937 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -310,6 +310,8 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, int ret;
if (flags & RSEQ_FLAG_UNREGISTER) { + if (flags & ~RSEQ_FLAG_UNREGISTER) + return -EINVAL; /* Unregister rseq for current thread. */ if (current->rseq != rseq || !current->rseq) return -EINVAL;
It has been reported by Google that rseq is not behaving properly with respect to clone when CLONE_VM is used without CLONE_THREAD. It keeps the prior thread's rseq TLS registered when the TLS of the thread has moved, so the kernel can corrupt the TLS of the parent.
The approach of clearing the per task-struct rseq registration on clone with CLONE_THREAD flag is incomplete. It does not cover the use-case of clone with CLONE_VM set, but without CLONE_THREAD.
Here is the rationale for unregistering rseq on clone with CLONE_VM flag set:
1) CLONE_THREAD requires CLONE_SIGHAND, which requires CLONE_VM to be set. Therefore, just checking for CLONE_VM covers all CLONE_THREAD uses. There is no point in checking for both CLONE_THREAD and CLONE_VM,
2) There is the possibility of an unlikely scenario where CLONE_SETTLS is used without CLONE_VM. In order to be an issue, it would require that the rseq TLS is in a shared memory area.
I do not plan on adding CLONE_SETTLS to the set of clone flags which unregister RSEQ, because it would require that we also unregister RSEQ on set_thread_area(2) and arch_prctl(2) ARCH_SET_FS for completeness. So rather than doing a partial solution, it appears better to let user-space explicitly perform rseq unregistration across clone if needed in scenarios where CLONE_VM is not set.
Signed-off-by: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Peter Zijlstra (Intel) peterz@infradead.org Cc: "Paul E. McKenney" paulmck@linux.ibm.com Cc: Boqun Feng boqun.feng@gmail.com Cc: "H . Peter Anvin" hpa@zytor.com Cc: Paul Turner pjt@google.com Cc: Dmitry Vyukov dvyukov@google.com Cc: Neel Natu neelnatu@google.com Cc: linux-api@vger.kernel.org Cc: stable@vger.kernel.org # v4.18+ --- include/linux/sched.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h index 9f51932bd543..d1eab0012af1 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1919,11 +1919,11 @@ static inline void rseq_migrate(struct task_struct *t)
/* * If parent process has a registered restartable sequences area, the - * child inherits. Only applies when forking a process, not a thread. + * child inherits. Unregister rseq for a clone with CLONE_VM set. */ static inline void rseq_fork(struct task_struct *t, unsigned long clone_flags) { - if (clone_flags & CLONE_THREAD) { + if (clone_flags & CLONE_VM) { t->rseq = NULL; t->rseq_sig = 0; t->rseq_event_mask = 0;
glibc 2.30 introduces gettid() in public headers, which clashes with the internal static definition within rseq selftests.
Rename gettid() to rseq_gettid() to eliminate this symbol name clash.
Reported-by: Tommi T. Rantala tommi.t.rantala@nokia.com Signed-off-by: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Shuah Khan skhan@linuxfoundation.org Cc: Tommi T. Rantala tommi.t.rantala@nokia.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Peter Zijlstra (Intel) peterz@infradead.org Cc: "Paul E. McKenney" paulmck@linux.ibm.com Cc: Boqun Feng boqun.feng@gmail.com Cc: "H . Peter Anvin" hpa@zytor.com Cc: Paul Turner pjt@google.com Cc: Dmitry Vyukov dvyukov@google.com Cc: stable@vger.kernel.org # v4.18+ --- tools/testing/selftests/rseq/param_test.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/tools/testing/selftests/rseq/param_test.c b/tools/testing/selftests/rseq/param_test.c index eec2663261f2..e8a657a5f48a 100644 --- a/tools/testing/selftests/rseq/param_test.c +++ b/tools/testing/selftests/rseq/param_test.c @@ -15,7 +15,7 @@ #include <errno.h> #include <stddef.h>
-static inline pid_t gettid(void) +static inline pid_t rseq_gettid(void) { return syscall(__NR_gettid); } @@ -373,11 +373,12 @@ void *test_percpu_spinlock_thread(void *arg) rseq_percpu_unlock(&data->lock, cpu); #ifndef BENCHMARK if (i != 0 && !(i % (reps / 10))) - printf_verbose("tid %d: count %lld\n", (int) gettid(), i); + printf_verbose("tid %d: count %lld\n", + (int) rseq_gettid(), i); #endif } printf_verbose("tid %d: number of rseq abort: %d, signals delivered: %u\n", - (int) gettid(), nr_abort, signals_delivered); + (int) rseq_gettid(), nr_abort, signals_delivered); if (!opt_disable_rseq && thread_data->reg && rseq_unregister_current_thread()) abort(); @@ -454,11 +455,12 @@ void *test_percpu_inc_thread(void *arg) } while (rseq_unlikely(ret)); #ifndef BENCHMARK if (i != 0 && !(i % (reps / 10))) - printf_verbose("tid %d: count %lld\n", (int) gettid(), i); + printf_verbose("tid %d: count %lld\n", + (int) rseq_gettid(), i); #endif } printf_verbose("tid %d: number of rseq abort: %d, signals delivered: %u\n", - (int) gettid(), nr_abort, signals_delivered); + (int) rseq_gettid(), nr_abort, signals_delivered); if (!opt_disable_rseq && thread_data->reg && rseq_unregister_current_thread()) abort(); @@ -605,7 +607,7 @@ void *test_percpu_list_thread(void *arg) }
printf_verbose("tid %d: number of rseq abort: %d, signals delivered: %u\n", - (int) gettid(), nr_abort, signals_delivered); + (int) rseq_gettid(), nr_abort, signals_delivered); if (!opt_disable_rseq && rseq_unregister_current_thread()) abort();
@@ -796,7 +798,7 @@ void *test_percpu_buffer_thread(void *arg) }
printf_verbose("tid %d: number of rseq abort: %d, signals delivered: %u\n", - (int) gettid(), nr_abort, signals_delivered); + (int) rseq_gettid(), nr_abort, signals_delivered); if (!opt_disable_rseq && rseq_unregister_current_thread()) abort();
@@ -1011,7 +1013,7 @@ void *test_percpu_memcpy_buffer_thread(void *arg) }
printf_verbose("tid %d: number of rseq abort: %d, signals delivered: %u\n", - (int) gettid(), nr_abort, signals_delivered); + (int) rseq_gettid(), nr_abort, signals_delivered); if (!opt_disable_rseq && rseq_unregister_current_thread()) abort();
Hi Thomas,
I thought those rseq fixes posted in September were in the -tip tree, but it seems that they never made it to mainline.
Now Shuah Khan noticed the issue with gettid() compatibility with glibc 2.30+. This series contained that fix.
Should I re-post it, or is this series on track to get into mainline at some point ?
Thanks,
Mathieu
----- On Sep 17, 2019, at 2:29 PM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:
Hi,
Here is a small set of rseq fixes aiming Linux 5.4. Those should be backported to stable kernels >= 4.18.
Thanks,
Mathieu
Mathieu Desnoyers (3): rseq: Fix: Reject unknown flags on rseq unregister rseq: Fix: Unregister rseq for clone CLONE_VM rseq/selftests: Fix: Namespace gettid() for compatibility with glibc 2.30
include/linux/sched.h | 4 ++-- kernel/rseq.c | 2 ++ tools/testing/selftests/rseq/param_test.c | 18 ++++++++++-------- 3 files changed, 14 insertions(+), 10 deletions(-)
-- 2.17.1
On 12/11/19 8:28 AM, Mathieu Desnoyers wrote:
Hi Thomas,
I thought those rseq fixes posted in September were in the -tip tree, but it seems that they never made it to mainline.
Now Shuah Khan noticed the issue with gettid() compatibility with glibc 2.30+. This series contained that fix.
Should I re-post it, or is this series on track to get into mainline at some point ?
It will be great this can make it into 5.5-rc2 or so.
thanks, -- Shuah
On 12/11/19 8:47 AM, Shuah Khan wrote:
On 12/11/19 8:28 AM, Mathieu Desnoyers wrote:
Hi Thomas,
I thought those rseq fixes posted in September were in the -tip tree, but it seems that they never made it to mainline.
Now Shuah Khan noticed the issue with gettid() compatibility with glibc 2.30+. This series contained that fix.
Should I re-post it, or is this series on track to get into mainline at some point ?
It will be great this can make it into 5.5-rc2 or so.
thanks, -- Shuah
I am pulling this patch in for Linux 5.5-rc4.
Let me know if you have any objections.
thanks, -- Shuah
linux-stable-mirror@lists.linaro.org
-
Mathieu Desnoyers -
Shuah Khan