Messages in this thread Patch in this message | | | From | Edward Adam Davis <> | Subject | [PATCH v2] drm/atomic-helpers: fix uaf in drm_atomic_helper_wait_for_vblanks | Date | Thu, 15 Feb 2024 23:12:29 +0800 |
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To briefly summarize the issues reported by syzbot, there are two task call stacks as follows:
Task A Task B ------------------------------------ ---------------------------------- drm_atomic_commit drm_atomic_helper_commit commit_work commit_tail drm_atomic_helper_commit_tail commit_tail drm_atomic_helper_commit_tail drm_client_modeset_commit_atomic drm_atomic_state_default_clear drm_atomic_helper_wait_for_vblanks
When two prerequisites are met simultaneously, the current issue will be triggered: 1. There is an overlap in the memory range occupied by the crtcs member set contained in the instance state of "struct drm_atomic_state" created by Task A and Task B 2. The context of drm_atomic_helper_commit_tail() has no lock protection, resulting in the instance state->crtcs sub item being released by other task
The solution is to add a lock in drm_atomic_helper_commit_tail() to ensure that there is no other task interference when accessing the instance state.
Reported-and-tested-by: syzbot+0f999d26a4fd79c3a23b@syzkaller.appspotmail.com Signed-off-by: Edward Adam Davis <eadavis@qq.com> --- drivers/gpu/drm/drm_atomic_helper.c | 3 +++ 1 file changed, 3 insertions(+)
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); -- 2.43.0
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