From: Mikita Lipski mikita.lipski@amd.com
Use drm_atomic_get_crtc_state to get the crtc state in case it has been previously freed, that might prevent use-after-free issue.
This patch fixes the bugzilla bug: Bug 199425 - BUG: KASAN: use-after-free in drm_atomic_helper_wait_for_flip_done+0x247/0x260
Signed-off-by: Mikita Lipski mikita.lipski@amd.com --- drivers/gpu/drm/drm_atomic_helper.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c index e8c2493..e083f85 100644 --- a/drivers/gpu/drm/drm_atomic_helper.c +++ b/drivers/gpu/drm/drm_atomic_helper.c @@ -1276,9 +1276,11 @@ void drm_atomic_helper_wait_for_flip_done(struct drm_device *dev, int i;
for_each_new_crtc_in_state(old_state, crtc, new_crtc_state, i) { - struct drm_crtc_commit *commit = new_crtc_state->commit; + struct drm_crtc_commit *commit; int ret;
+ new_crtc_state = drm_atomic_get_crtc_state(old_state, crtc); + commit = new_crtc_state->commit; if (!commit) continue;
Hi Mikita,
thanks for sending this out. I have to defer review of the actual change to others more familiar with this code, but I have some feedback for the commit log.
On 2018-06-19 04:45 PM, mikita.lipski@amd.com wrote:
Bug reports are referenced like this:
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199425
Also, as the issue exists since at least 4.17, this should have
Cc: stable@vger.kernel.org
in order for the fix to be backported to stable branches.
On Tue, Jun 19, 2018 at 10:45:31AM -0400, mikita.lipski@amd.com wrote:
Uh no. wait_for_flip done is supposed to be called from the ->atomic_commit hook, and duplicating state objects (as is done by the various get_foo_state functions) is only allowed from the ->atomic_check hook. What that blows up for you, this isn't the fix you're looking for. Aside: get_foo_state can fail, the __must_check annotation should have been a hint for that.
For starters it would be useful if you include the full details of what's going boom in the amdgpu driver for you. -Daniel
On Tue, Jun 19, 2018 at 05:27:57PM +0200, Daniel Vetter wrote:
From a quick glance at the bug report it looks like a cursor update
getting ahead of a page flip.
Actually I'm not even sure how this manages to work on i915. On i915 we allow the cursor update to go through as soon as hw_done is completed. That would seem to mean that all the cleanup work commit_tail does afterwards is at risk of using a freed plane state. Well, maybe. The way this is all implemented doesn't really agree with my brain so I can't be 100% sure.
Whacking a big sleep just after drm_atomic_helper_commit_hw_done() should be able to confirm that I suppose.
dri-devel@lists.freedesktop.org
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