[PATCH] perf: fix put_event() ctx leak

[PATCH] perf: fix put_event() ctx leak

[Leon Yu]

Commit a83fe28e2e45 ("perf: Fix put_event() ctx lock") changed lock logic in
put_event() by replacing mutex_lock_nested() with perf_event_ctx_lock_nested(),
but didn't fix subsequent mutex_unlock() with correct counterpart,
perf_event_ctx_unlock(). ctx is thus leaked as a result of incremented
refcount in perf_event_ctx_lock_nested().

Signed-off-by: Leon Yu <chianglungyu@gmail.com>
Fixes: a83fe28e2e45 ("perf: Fix put_event() ctx lock")
---
 kernel/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index f04daab..453ef61 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3591,7 +3591,7 @@ static void put_event(struct perf_event *event)
 	ctx = perf_event_ctx_lock_nested(event, SINGLE_DEPTH_NESTING);
 	WARN_ON_ONCE(ctx->parent_ctx);
 	perf_remove_from_context(event, true);
-	mutex_unlock(&ctx->mutex);
+	perf_event_ctx_unlock(event, ctx);
 
 	_free_event(event);
 }
-- 
2.3.1

Re: [PATCH] perf: fix put_event() ctx leak

[Leon Yu]

On Thu, Feb 26, 2015 at 8:43 PM, Leon Yu <chianglungyu@gmail.com> wrote:
>
> Commit a83fe28e2e45 ("perf: Fix put_event() ctx lock") changed lock logic in
> put_event() by replacing mutex_lock_nested() with perf_event_ctx_lock_nested(),
> but didn't fix subsequent mutex_unlock() with correct counterpart,
> perf_event_ctx_unlock(). ctx is thus leaked as a result of incremented
> refcount in perf_event_ctx_lock_nested().
>
> Signed-off-by: Leon Yu <chianglungyu@gmail.com>
> Fixes: a83fe28e2e45 ("perf: Fix put_event() ctx lock")
> ---
>  kernel/events/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index f04daab..453ef61 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -3591,7 +3591,7 @@ static void put_event(struct perf_event *event)
>         ctx = perf_event_ctx_lock_nested(event, SINGLE_DEPTH_NESTING);
>         WARN_ON_ONCE(ctx->parent_ctx);
>         perf_remove_from_context(event, true);
> -       mutex_unlock(&ctx->mutex);
> +       perf_event_ctx_unlock(event, ctx);
>
>         _free_event(event);
>  }

Gentle ping.

It has been two weeks since previous post, the issue remains un-fixed
and affects some more users [1].
It would be very appreciated if I can get some responses from related
maintainers since we're almost
half way to release.

[1] http://marc.info/?l=linux-kernel&m=142618052120848&w=2

-Leon

[tip:perf/urgent] perf: Fix context leak in put_event()

[tip-bot for Leon Yu]

Commit-ID:  d415a7f1c1a8406b22d95b943c66a5b73a37bc19
Gitweb:     http://git.kernel.org/tip/d415a7f1c1a8406b22d95b943c66a5b73a37bc19
Author:     Leon Yu <chianglungyu@gmail.com>
AuthorDate: Thu, 26 Feb 2015 20:43:33 +0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 13 Mar 2015 10:02:18 +0100

perf: Fix context leak in put_event()

Commit:

  a83fe28e2e45 ("perf: Fix put_event() ctx lock")

changed the locking logic in put_event() by replacing mutex_lock_nested()
with perf_event_ctx_lock_nested(), but didn't fix the subsequent
mutex_unlock() with a correct counterpart, perf_event_ctx_unlock().

Contexts are thus leaked as a result of incremented refcount
in perf_event_ctx_lock_nested().

Signed-off-by: Leon Yu <chianglungyu@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Fixes: a83fe28e2e45 ("perf: Fix put_event() ctx lock")
Link: http://lkml.kernel.org/r/1424954613-5034-1-git-send-email-chianglungyu@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index f04daab..453ef61 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3591,7 +3591,7 @@ static void put_event(struct perf_event *event)
 	ctx = perf_event_ctx_lock_nested(event, SINGLE_DEPTH_NESTING);
 	WARN_ON_ONCE(ctx->parent_ctx);
 	perf_remove_from_context(event, true);
-	mutex_unlock(&ctx->mutex);
+	perf_event_ctx_unlock(event, ctx);
 
 	_free_event(event);
 }