linux-kernel - Re: [syzbot] [dri?] KASAN: slab-use-after-free Read in drm_atomic_helper_wait_for

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Date: Thu, 15 Feb 2024 18:15:16 +0800
From: Edward Adam Davis <eadavis@...com>
To: syzbot+0f999d26a4fd79c3a23b@...kaller.appspotmail.com
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [dri?] KASAN: slab-use-after-free Read in drm_atomic_helper_wait_for_vblanks (2)

please test uaf in drm_atomic_helper_wait_for_vblanks

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 39ef0a6addeb..b16ff9020097 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1743,7 +1743,9 @@ EXPORT_SYMBOL(drm_atomic_helper_wait_for_flip_done);
 void drm_atomic_helper_commit_tail(struct drm_atomic_state *old_state)
 {
 	struct drm_device *dev = old_state->dev;
+	static DEFINE_MUTEX(lock);
 
+	mutex_lock(&lock);
 	drm_atomic_helper_commit_modeset_disables(dev, old_state);
 
 	drm_atomic_helper_commit_planes(dev, old_state, 0);
@@ -1757,6 +1759,7 @@ void drm_atomic_helper_commit_tail(struct drm_atomic_state *old_state)
 	drm_atomic_helper_wait_for_vblanks(dev, old_state);
 
 	drm_atomic_helper_cleanup_planes(dev, old_state);
+	mutex_unlock(&lock);
 }
 EXPORT_SYMBOL(drm_atomic_helper_commit_tail);