[PATCH] perf: fix event leak when perf_event_open() failed to create event_file

[PATCH] perf: fix event leak when perf_event_open() failed to create event_file

[Leon Yu]

If something went wrong in anon_inode_getfile, event_file will be set to
non-zero error number and able to bypass the NULL test afterward.

Consolidate the error path by testing event_file with handly
IS_ERR_OR_NULL() helper since we do want to free event in both cases.

Signed-off-by: Leon Yu <chianglungyu@gmail.com>
Fixes: 130056275ade ("perf: Do not double free")
Cc: <stable@vger.kernel.org> # v4.5
---
 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 6146148..5f2e19f 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8617,7 +8617,7 @@ err_alloc:
 	 * If event_file is set, the fput() above will have called ->release()
 	 * and that will take care of freeing the event.
 	 */
-	if (!event_file)
+	if (IS_ERR_OR_NULL(event_file))
 		free_event(event);
 err_cpus:
 	put_online_cpus();
-- 
2.7.1

Re: [PATCH] perf: fix event leak when perf_event_open() failed to create event_file

[Alexander Shishkin]

Leon Yu <chianglungyu@gmail.com> writes:

> If something went wrong in anon_inode_getfile, event_file will be set to
> non-zero error number and able to bypass the NULL test afterward.
>
> Consolidate the error path by testing event_file with handly
> IS_ERR_OR_NULL() helper since we do want to free event in both cases.
>
> Signed-off-by: Leon Yu <chianglungyu@gmail.com>
> Fixes: 130056275ade ("perf: Do not double free")
> Cc: <stable@vger.kernel.org> # v4.5
> ---
>  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 6146148..5f2e19f 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -8617,7 +8617,7 @@ err_alloc:
>  	 * If event_file is set, the fput() above will have called ->release()
>  	 * and that will take care of freeing the event.
>  	 */
> -	if (!event_file)
> +	if (IS_ERR_OR_NULL(event_file))
>  		free_event(event);

By this time, we have already checked for IS_ERR(event_file) once, why
not just fix it up there like so:

---
From: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Date: Mon, 21 Mar 2016 09:55:09 +0200
Subject: perf: Don't leak event in the syscall error path

In the error path, event_file not being NULL is used to determine
whether the event itself still needs to be free'd, so fix it up to avoid
leaking.

Reported-by: Leon Yu <chianglungyu@gmail.com>
Fixes: 130056275ade ("perf: Do not double free")
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
---
 kernel/events/core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index ab83640a50..cc34d55f1e 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9414,6 +9414,7 @@ SYSCALL_DEFINE5(perf_event_open,
 					f_flags);
 	if (IS_ERR(event_file)) {
 		err = PTR_ERR(event_file);
+		event_file = NULL;
 		goto err_context;
 	}
 
-- 
2.7.0

Re: [PATCH] perf: fix event leak when perf_event_open() failed to create event_file

[Leon Yu]

On Mon, Mar 21, 2016 at 4:02 PM, Alexander Shishkin
<alexander.shishkin@linux.intel.com> wrote:
> Leon Yu <chianglungyu@gmail.com> writes:
>
>> If something went wrong in anon_inode_getfile, event_file will be set to
>> non-zero error number and able to bypass the NULL test afterward.
>>
>> Consolidate the error path by testing event_file with handly
>> IS_ERR_OR_NULL() helper since we do want to free event in both cases.
>>
>> Signed-off-by: Leon Yu <chianglungyu@gmail.com>
>> Fixes: 130056275ade ("perf: Do not double free")
>> Cc: <stable@vger.kernel.org> # v4.5
>> ---
>>  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 6146148..5f2e19f 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -8617,7 +8617,7 @@ err_alloc:
>>        * If event_file is set, the fput() above will have called ->release()
>>        * and that will take care of freeing the event.
>>        */
>> -     if (!event_file)
>> +     if (IS_ERR_OR_NULL(event_file))
>>               free_event(event);
>
> By this time, we have already checked for IS_ERR(event_file) once, why
> not just fix it up there like so:

My patch is more straightforward, isn't it? :p
Anyway I don't mind which one will get merged as long as the problem is fixed.

(sorry forgot to CC all recipients)

-Leon

> @@ -9414,6 +9414,7 @@ SYSCALL_DEFINE5(perf_event_open,
>                                         f_flags);
>         if (IS_ERR(event_file)) {
>                 err = PTR_ERR(event_file);
> +               event_file = NULL;
>                 goto err_context;
>         }
>
> --
> 2.7.0
>

[tip:perf/core] perf/core: Don't leak event in the syscall error path

[tip-bot for Alexander Shishkin]

Commit-ID:  201c2f85bd0bc13b712d9c0b3d11251b182e06ae
Gitweb:     http://git.kernel.org/tip/201c2f85bd0bc13b712d9c0b3d11251b182e06ae
Author:     Alexander Shishkin <alexander.shishkin@linux.intel.com>
AuthorDate: Mon, 21 Mar 2016 10:02:42 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 31 Mar 2016 09:54:07 +0200

perf/core: Don't leak event in the syscall error path

In the error path, event_file not being NULL is used to determine
whether the event itself still needs to be free'd, so fix it up to
avoid leaking.

Reported-by: Leon Yu <chianglungyu@gmail.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Fixes: 130056275ade ("perf: Do not double free")
Link: http://lkml.kernel.org/r/87twk06yxp.fsf@ashishki-desk.ger.corp.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/events/core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 8c11388..52bedc5 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8542,6 +8542,7 @@ SYSCALL_DEFINE5(perf_event_open,
 					f_flags);
 	if (IS_ERR(event_file)) {
 		err = PTR_ERR(event_file);
+		event_file = NULL;
 		goto err_context;
 	}