Hi Greg,
After investigating the follow-on patch, current commit 517e6a301f34 ("perf: Fix perf_pending_task() UaF") needs
to backport the following commits:
Commit 3a5465418f5f ("perf: Fix event leak upon exec and file release") -- Fix commit 517e6a301f34
Commit 56799bc03565 ("perf: Fix hang while freeing sigtrap event") -- Fix commit 56799bc03565
For the commit 3a5465418f5f ("perf: Fix event leak upon exec and file release"), it depends on commit ca6c21327c6a ("perf: Fix missing SIGTRAPs"),
but commit ca6c21327c6a ("perf: Fix missing SIGTRAPs") based on Commit 97ba62b27867 ("perf: Add support for SIGTRAP on perf events") which is a new
feature intruduced since kernel 5.13-rc1, and the new feature changed the perf_event.h in uapi.
Fully backport the current commit and the follow-on patches too risky for a stable branch, so please ignore current patch, that
might cause more bugs for 5.10, thanks :)
Br,
Xiangyu
On 4/24/25 14:33, Xiangyu Chen wrote:
Hi Greg,
On 4/23/25 22:15, Greg KH wrote:
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On Tue, Apr 08, 2025 at 02:10:44PM +0800, Xiangyu Chen wrote:
From: Peter Zijlstra peterz@infradead.org
[ Upstream commit 517e6a301f34613bff24a8e35b5455884f2d83d8 ]
Per syzbot it is possible for perf_pending_task() to run after the event is free()'d. There are two related but distinct cases:
- the task_work was already queued before destroying the event; - destroying the event itself queues the task_work.
The first cannot be solved using task_work_cancel() since perf_release() itself might be called from a task_work (____fput), which means the current->task_works list is already empty and task_work_cancel() won't be able to find the perf_pending_task() entry.
The simplest alternative is extending the perf_event lifetime to cover the task_work.
The second is just silly, queueing a task_work while you know the event is going away makes no sense and is easily avoided by re-arranging how the event is marked STATE_DEAD and ensuring it goes through STATE_OFF on the way down.
Reported-by: syzbot+9228d6098455bb209ec8@syzkaller.appspotmail.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Tested-by: Marco Elver elver@google.com [ Discard the changes in event_sched_out() due to 5.10 don't have the commit: 97ba62b27867 ("perf: Add support for SIGTRAP on perf events") and commit: ca6c21327c6a ("perf: Fix missing SIGTRAPs") ] Signed-off-by: Xiangyu Chen xiangyu.chen@windriver.com Signed-off-by: He Zhe zhe.he@windriver.com
Verified the build test.
You missed all of the fix-up patches for this commit that happened after it, fixing memory leaks and the like. So if we applied this, we would have more bugs added to the tree than fixed :(
ALWAYS check for follow-on fixes.
I'll go drop this.
Thanks for your info, I have checked the full log and there is another commit to fix current commit,
Please ignore this patch , I will try to backport the fixes to 5.10 and resend the review to list after local testing.
Thanks.
Br,
Xiangyu
greg k-h