drm/panthor: Fix race condition when gathering fdinfo group samples

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.

Fixes: e16635d88fa0 ("drm/panthor: add DRM fdinfo support")
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250130172851.941597-6-adrian.larumbe@collabora.com
Link: https://patchwork.freedesktop.org/patch/msgid/20250107173310.88329-1-florent.tomasin@arm.com

diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
index da87e6e819387decb2a06fa54152a338742aa3c5..0b93bf83a9b21f225602a41be8b6ea9b01b05172 100644 (file)
--- a/drivers/gpu/drm/panthor/panthor_sched.c
+++ b/drivers/gpu/drm/panthor/panthor_sched.c
@@ -2878,6 +2878,7 @@ 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;
@@ -2886,6 +2887,7 @@ 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)