diff options
Diffstat (limited to '0004-drm-amd-display-Clear-dm_state-for-fast-updates.patch')
| -rw-r--r-- | 0004-drm-amd-display-Clear-dm_state-for-fast-updates.patch | 97 |
1 files changed, 0 insertions, 97 deletions
diff --git a/0004-drm-amd-display-Clear-dm_state-for-fast-updates.patch b/0004-drm-amd-display-Clear-dm_state-for-fast-updates.patch deleted file mode 100644 index 8608e91..0000000 --- a/0004-drm-amd-display-Clear-dm_state-for-fast-updates.patch +++ /dev/null @@ -1,97 +0,0 @@ -From 6ab7cba72fbdc4eb3c3547eb278924e06dd68fe4 Mon Sep 17 00:00:00 2001 -From: Mazin Rezk <mnrzk@protonmail.com> -Date: Mon, 27 Jul 2020 05:40:46 +0000 -Subject: 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: bd200d190f45 ("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> ---- - drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 36 +++++++++++++++++------ - 1 file changed, 27 insertions(+), 9 deletions(-) - -diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c -index 837a286469ec..d50751ae73f1 100644 ---- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c -+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c -@@ -8489,20 +8489,38 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev, - * the same resource. If we have a new DC context as part of - * the DM atomic state from validation we need to free it and - * retain the existing one instead. -+ * -+ * Furthermore, since the DM atomic state only contains the DC -+ * context and can safely be annulled, we can free the state -+ * and clear the associated private object now to free -+ * some memory and avoid a possible use-after-free later. - */ -- struct dm_atomic_state *new_dm_state, *old_dm_state; - -- new_dm_state = dm_atomic_get_new_state(state); -- old_dm_state = dm_atomic_get_old_state(state); -+ for (i = 0; i < state->num_private_objs; i++) { -+ struct drm_private_obj *obj = state->private_objs[i].ptr; - -- if (new_dm_state && old_dm_state) { -- if (new_dm_state->context) -- dc_release_state(new_dm_state->context); -+ if (obj->funcs == adev->dm.atomic_obj.funcs) { -+ int j = state->num_private_objs-1; - -- new_dm_state->context = old_dm_state->context; -+ dm_atomic_destroy_state(obj, -+ state->private_objs[i].state); -+ -+ /* If i is not at the end of the array then the -+ * last element needs to be moved to where i was -+ * before the array can safely be truncated. -+ */ -+ if (i != j) -+ state->private_objs[i] = -+ state->private_objs[j]; - -- if (old_dm_state->context) -- dc_retain_state(old_dm_state->context); -+ state->private_objs[j].ptr = NULL; -+ state->private_objs[j].state = NULL; -+ state->private_objs[j].old_state = NULL; -+ state->private_objs[j].new_state = NULL; -+ -+ state->num_private_objs = j; -+ break; -+ } - } - } - --- -cgit v1.2.3-1-gf6bb5 - |