From: Daniel Vetter daniel.vetter@ffwll.ch
commit a37eef63bc9e16e06361b539e528058146af80ab 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: bc9c80fe01a2 ("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... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/gpu/drm/drm_syncobj.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
--- a/drivers/gpu/drm/drm_syncobj.c +++ b/drivers/gpu/drm/drm_syncobj.c @@ -326,19 +326,18 @@ int drm_syncobj_find_fence(struct drm_fi 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; @@ -370,6 +369,9 @@ int drm_syncobj_find_fence(struct drm_fi if (wait.node.next) drm_syncobj_remove_wait(syncobj, &wait);
+out: + drm_syncobj_put(syncobj); + return ret; } EXPORT_SYMBOL(drm_syncobj_find_fence);