Mazin Rezk fde9f39ac7 drm/amd/display: Clear dm_state for fast updates ... This patch fixes a race condition that causes a use-after-free during amdgpu_dm_atomic_commit_tail. This can occur when 2 non-blocking commits are requested and the second one finishes before the first. Essentially, this bug occurs when the following sequence of events happens: 1. Non-blocking commit #1 is requested w/ a new dm_state #1 and is deferred to the workqueue. 2. Non-blocking commit #2 is requested w/ a new dm_state #2 and is deferred to the workqueue. 3. Commit #2 starts before commit #1, dm_state #1 is used in the commit_tail and commit #2 completes, freeing dm_state #1. 4. Commit #1 starts after commit #2 completes, uses the freed dm_state 1 and dereferences a freelist pointer while setting the context. Since this bug has only been spotted with fast commits, this patch fixes the bug by clearing the dm_state instead of using the old dc_state for fast updates. In addition, since dm_state is only used for its dc_state and amdgpu_dm_atomic_commit_tail will retain the dc_state if none is found, removing the dm_state should not have any consequences in fast updates. This use-after-free bug has existed for a while now, but only caused a noticeable issue starting from 5.7-rc1 due to 3202fa62f ("slub: relocate freelist pointer to middle of object") moving the freelist pointer from dm_state->base (which was unused) to dm_state->context (which is dereferenced). Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=207383 Fixes: bd200d190f ("drm/amd/display: Don't replace the dc_state for fast updates") Reported-by: Duncan <1i5t5.duncan@cox.net> Signed-off-by: Mazin Rezk <mnrzk@protonmail.com> Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> Cc: stable@vger.kernel.org		2020-07-30 11:02:10 -04:00
..
amdgpu_dm	drm/amd/display: Clear dm_state for fast updates	2020-07-30 11:02:10 -04:00
dc	drm/amd/display: handle failed allocation during stream construction	2020-07-14 15:14:15 -04:00
dmub	drm/amd/display: Add struct field for future use	2020-05-05 13:12:40 -04:00
include	drm/amd/display: query hdcp capability during link detect	2020-04-09 10:43:17 -04:00
modules	drm/amd/display: Use kfree() to free rgb_user in calculate_user_regamma_ramp()	2020-06-10 18:00:24 -04:00
Kconfig	drm: amd/display: fix Kconfig help text	2020-04-23 15:06:41 -04:00
Makefile
TODO