drm: Fix authentication kernel crash

If the master tries to authenticate a client using drm_authmagic and
that client has already closed its drm file descriptor,
either wilfully or because it was terminated, the
call to drm_authmagic will dereference a stale pointer into kmalloc'ed memory
and corrupt it.

Typically this results in a hard system hang.

This patch fixes that problem by removing any authentication tokens
(struct drm_magic_entry) open for a file descriptor when that file
descriptor is closed.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 76caa67c22e2..92f0981b5fb8 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1328,6 +1328,7 @@ extern int drm_getmagic(struct drm_device *dev, void *data,
                         struct drm_file *file_priv);
 extern int drm_authmagic(struct drm_device *dev, void *data,
                          struct drm_file *file_priv);
+extern int drm_remove_magic(struct drm_master *master, drm_magic_t magic);
 
 /* Cache management (drm_cache.c) */
 void drm_clflush_pages(struct page *pages[], unsigned long num_pages);