[PATCH for 5.5 0/3] Restartable Sequences Fixes

[PATCH for 5.5 0/3] Restartable Sequences Fixes

[Mathieu Desnoyers]

Hi,

Here is a repost of a small set of rseq fixes which was initially posted
in September 2019. It now targets kernel 5.5. 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

[PATCH for 5.5 1/3] rseq: Fix: Reject unknown flags on rseq unregister

[Mathieu Desnoyers]

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;
-- 
2.17.1

[PATCH for 5.5 2/3] rseq: Fix: Unregister rseq for clone CLONE_VM

[Mathieu Desnoyers]

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 467d26046416..716ad1d8d95e 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1929,11 +1929,11 @@ 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;
-- 
2.17.1

[PATCH for 5.5 3/3] rseq/selftests: Fix: Namespace gettid() for compatibility with glibc 2.30

[Mathieu Desnoyers]

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();
 
-- 
2.17.1

Re: [PATCH for 5.5 3/3] rseq/selftests: Fix: Namespace gettid() for compatibility with glibc 2.30

[Shuah Khan]

On 12/11/19 9:17 AM, Mathieu Desnoyers wrote:
> 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 ++++++++++--------


I am pulling this patch in for Linux 5.5-rc4.

Let me know if you have any objections.

thanks,
-- Shuah

Re: [PATCH for 5.5 0/3] Restartable Sequences Fixes

[Peter Zijlstra]

On Wed, Dec 11, 2019 at 11:17:10AM -0500, Mathieu Desnoyers wrote:
> Hi,
> 
> Here is a repost of a small set of rseq fixes which was initially posted
> in September 2019. It now targets kernel 5.5. 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

I've picked up the first two patches, thanks!

[tip: core/urgent] rseq: Unregister rseq for clone CLONE_VM

[tip-bot2 for Mathieu Desnoyers]

The following commit has been merged into the core/urgent branch of tip:

Commit-ID:     463f550fb47bede3a5d7d5177f363a6c3b45d50b
Gitweb:        https://git.kernel.org/tip/463f550fb47bede3a5d7d5177f363a6c3b45d50b
Author:        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
AuthorDate:    Wed, 11 Dec 2019 11:17:12 -05:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 25 Dec 2019 10:41:20 +01:00

rseq: Unregister rseq for clone CLONE_VM

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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191211161713.4490-3-mathieu.desnoyers@efficios.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 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 467d260..716ad1d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1929,11 +1929,11 @@ 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;

[tip: core/urgent] rseq: Reject unknown flags on rseq unregister

[tip-bot2 for Mathieu Desnoyers]

The following commit has been merged into the core/urgent branch of tip:

Commit-ID:     66528a4575eee9f5a5270219894ab6178f146e84
Gitweb:        https://git.kernel.org/tip/66528a4575eee9f5a5270219894ab6178f146e84
Author:        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
AuthorDate:    Wed, 11 Dec 2019 11:17:11 -05:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 25 Dec 2019 10:41:20 +01:00

rseq: Reject unknown flags on rseq unregister

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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191211161713.4490-2-mathieu.desnoyers@efficios.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/rseq.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/rseq.c b/kernel/rseq.c
index 27c48eb..a4f86a9 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;

Re: [tip: core/urgent] rseq: Reject unknown flags on rseq unregister

[Borislav Petkov]

On Wed, Dec 25, 2019 at 10:38:53AM -0000, tip-bot2 for Mathieu Desnoyers wrote:
> The following commit has been merged into the core/urgent branch of tip:
> 
> Commit-ID:     66528a4575eee9f5a5270219894ab6178f146e84
> Gitweb:        https://git.kernel.org/tip/66528a4575eee9f5a5270219894ab6178f146e84
> Author:        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> AuthorDate:    Wed, 11 Dec 2019 11:17:11 -05:00
> Committer:     Ingo Molnar <mingo@kernel.org>
> CommitterDate: Wed, 25 Dec 2019 10:41:20 +01:00
> 
> rseq: Reject unknown flags on rseq unregister
> 
> 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>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Link: https://lkml.kernel.org/r/20191211161713.4490-2-mathieu.desnoyers@efficios.com
> Signed-off-by: Ingo Molnar <mingo@kernel.org>
> ---
>  kernel/rseq.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/rseq.c b/kernel/rseq.c
> index 27c48eb..a4f86a9 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;

Cc: stable perhaps?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [tip: core/urgent] rseq: Reject unknown flags on rseq unregister

[Mathieu Desnoyers]

----- On Dec 25, 2019, at 6:39 AM, Borislav Petkov bp@alien8.de wrote:

> On Wed, Dec 25, 2019 at 10:38:53AM -0000, tip-bot2 for Mathieu Desnoyers wrote:
>> The following commit has been merged into the core/urgent branch of tip:
>> 
>> Commit-ID:     66528a4575eee9f5a5270219894ab6178f146e84
>> Gitweb:
>> https://git.kernel.org/tip/66528a4575eee9f5a5270219894ab6178f146e84
>> Author:        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
>> AuthorDate:    Wed, 11 Dec 2019 11:17:11 -05:00
>> Committer:     Ingo Molnar <mingo@kernel.org>
>> CommitterDate: Wed, 25 Dec 2019 10:41:20 +01:00
>> 
>> rseq: Reject unknown flags on rseq unregister
>> 
>> 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>
>> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>> Cc: Linus Torvalds <torvalds@linux-foundation.org>
>> Cc: Peter Zijlstra <peterz@infradead.org>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Link:
>> https://lkml.kernel.org/r/20191211161713.4490-2-mathieu.desnoyers@efficios.com
>> Signed-off-by: Ingo Molnar <mingo@kernel.org>
>> ---
>>  kernel/rseq.c | 2 ++
>>  1 file changed, 2 insertions(+)
>> 
>> diff --git a/kernel/rseq.c b/kernel/rseq.c
>> index 27c48eb..a4f86a9 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;
> 
> Cc: stable perhaps?

This could indeed be a candidate for stable, even though it's just a stricter
checking of unknown flags (returning an error rather than ignoring them).

Adding stable in CC here.

Thanks,

Mathieu


-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

Re: [tip: core/urgent] rseq: Reject unknown flags on rseq unregister

[Mathieu Desnoyers]

----- On Dec 26, 2019, at 5:32 PM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:

> ----- On Dec 25, 2019, at 6:39 AM, Borislav Petkov bp@alien8.de wrote:
> 
>> On Wed, Dec 25, 2019 at 10:38:53AM -0000, tip-bot2 for Mathieu Desnoyers wrote:
>>> The following commit has been merged into the core/urgent branch of tip:
>>> 
>>> Commit-ID:     66528a4575eee9f5a5270219894ab6178f146e84
>>> Gitweb:
>>> https://git.kernel.org/tip/66528a4575eee9f5a5270219894ab6178f146e84
>>> Author:        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
>>> AuthorDate:    Wed, 11 Dec 2019 11:17:11 -05:00
>>> Committer:     Ingo Molnar <mingo@kernel.org>
>>> CommitterDate: Wed, 25 Dec 2019 10:41:20 +01:00
>>> 
>>> rseq: Reject unknown flags on rseq unregister
>>> 
>>> 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>
>>> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>>> Cc: Linus Torvalds <torvalds@linux-foundation.org>
>>> Cc: Peter Zijlstra <peterz@infradead.org>
>>> Cc: Thomas Gleixner <tglx@linutronix.de>
>>> Link:
>>> https://lkml.kernel.org/r/20191211161713.4490-2-mathieu.desnoyers@efficios.com
>>> Signed-off-by: Ingo Molnar <mingo@kernel.org>
>>> ---
>>>  kernel/rseq.c | 2 ++
>>>  1 file changed, 2 insertions(+)
>>> 
>>> diff --git a/kernel/rseq.c b/kernel/rseq.c
>>> index 27c48eb..a4f86a9 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;
>> 
>> Cc: stable perhaps?
> 
> This could indeed be a candidate for stable, even though it's just a stricter
> checking of unknown flags (returning an error rather than ignoring them).
> 
> Adding stable in CC here.

For the records, I had stable in CC in my original patch submission. The stable CC has
been stripped when it was merged into the tip tree.

Thanks,

Mathieu

> 
> Thanks,
> 
> Mathieu
> 
> 
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

Re: [tip: core/urgent] rseq: Reject unknown flags on rseq unregister

[Peter Zijlstra]

On Mon, Jan 06, 2020 at 02:14:47PM -0500, Mathieu Desnoyers wrote:

> For the records, I had stable in CC in my original patch submission. The stable CC has
> been stripped when it was merged into the tip tree.

Argh, lemme go fix my scripts _again_..

I was recently made aware that we should not have spurious Cc: tags in
commit messages, but obviously the stable thing is an exception there.