Re: [PATCH v9 5/5] drm/panthor: Fix race condition when gathering fdinfo group samples

[Boris Brezillon <boris.brezillon@collabora.com>]

On Thu, 23 Jan 2025 22:53:02 +0000
Adrián Larumbe <adrian.larumbe@collabora.com> wrote:

> Commit e16635d88fa0 ("drm/panthor: add DRM fdinfo support") failed to
> protect access to groups with an xarray lock, which could lead to
> use-after-free errors.
> 
> Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
> Fixes: e16635d88fa0 ("drm/panthor: add DRM fdinfo support")

Nice catch!

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>

> ---
>  drivers/gpu/drm/panthor/panthor_sched.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> index e6c08a694e41..1d283b4bab86 100644
> --- a/drivers/gpu/drm/panthor/panthor_sched.c
> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> @@ -2865,6 +2865,7 @@ void panthor_fdinfo_gather_group_samples(struct panthor_file *pfile)
>  	if (IS_ERR_OR_NULL(gpool))
>  		return;
>  
> +	xa_lock(&gpool->xa);
>  	xa_for_each(&gpool->xa, i, group) {
>  		mutex_lock(&group->fdinfo.lock);
>  		pfile->stats.cycles += group->fdinfo.data.cycles;
> @@ -2873,6 +2874,7 @@ void panthor_fdinfo_gather_group_samples(struct panthor_file *pfile)
>  		group->fdinfo.data.time = 0;
>  		mutex_unlock(&group->fdinfo.lock);
>  	}
> +	xa_unlock(&gpool->xa);
>  }
>  
>  static void group_sync_upd_work(struct work_struct *work)