Re: [PATCH] signal: Prevent sigqueue caching after task got released

[Christian Brauner]

On Tue, Jun 22, 2021 at 01:08:30AM +0200, Thomas Gleixner wrote:
> syzbot reported a memory leak related to sigqueue caching. This happens
> when a thread group leader with child tasks is reaped.
> 
> The group leader's sigqueue_cache is correctly freed. The group leader then
> reaps the child tasks and if any of them has a signal pending it caches
> that signal. That's obviously bogus because nothing will free the cached
> signal of the reaped group leader anymore.
> 
> Prevent this by setting tsk::sigqueue_cache to an error pointer value in
> exit_task_sigqueue_cache().
> 
> Add comments to all relevant places.
> 
> Fixes: 4bad58ebc8bc ("signal: Allow tasks to cache one sigqueue struct")
> Reported-by: syzbot+0bac5fec63d4f399ba98@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> ---

Acked-by: Christian Brauner <christian.brauner@xxxxxxxxxx>