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drm/syncobj: Fix use-after-free

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commit a37eef63bc upstream.

While reviewing Christian's annotation patch I noticed that we have a
user-after-free for the WAIT_FOR_SUBMIT case: We drop the syncobj
reference before we've completed the waiting.

Of course usually there's nothing bad happening here since userspace
keeps the reference, but we can't rely on userspace to play nice here!

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Fixes: bc9c80fe01 ("drm/syncobj: use the timeline point in drm_syncobj_find_fence v4")
Reviewed-by: Christian König <christian.koenig@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v5.2+
Link: https://patchwork.freedesktop.org/patch/msgid/20210119130318.615145-1-daniel.vetter@ffwll.ch
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Daniel Vetter
2021-01-19 14:03:18 +01:00
committed by Greg Kroah-Hartman
parent 931bc41c59
commit eab4b3e274
1 changed files with 5 additions and 3 deletions
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8
drivers/gpu/drm/drm_syncobj.c
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@@ -388,19 +388,18 @@ int drm_syncobj_find_fence(struct drm_file *file_private,
return -ENOENT;
*fence = drm_syncobj_fence_get(syncobj);
drm_syncobj_put(syncobj);
if (*fence) {
ret = dma_fence_chain_find_seqno(fence, point);
if (!ret)
return 0;
goto out;
dma_fence_put(*fence);
} else {
ret = -EINVAL;
}
if (!(flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT))
return ret;
goto out;
memset(&wait, 0, sizeof(wait));
wait.task = current;
@@ -432,6 +431,9 @@ int drm_syncobj_find_fence(struct drm_file *file_private,
if (wait.node.next)
drm_syncobj_remove_wait(syncobj, &wait);
out:
drm_syncobj_put(syncobj);
return ret;
}
EXPORT_SYMBOL(drm_syncobj_find_fence);