On 18/6/21 1:03 am, Daniel Vetter wrote:
On Tue, Jun 15, 2021 at 10:36:44AM +0800, Desmond Cheong Zhi Xi wrote:
While checking the master status of the DRM file in
drm_is_current_master(), the device's master mutex should be
held. Without the mutex, the pointer fpriv->master may be freed
concurrently by another process calling drm_setmaster_ioctl(). This
could lead to use-after-free errors when the pointer is subsequently
dereferenced in drm_lease_owner().
The callers of drm_is_current_master() from drm_auth.c hold the
device's master mutex, but external callers do not. Hence, we implement
drm_is_current_master_locked() to be used within drm_auth.c, and
modify drm_is_current_master() to grab the device's master mutex
before checking the master status.
Reported-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@xxxxxxxxx>
Reviewed-by: Emil Velikov <emil.l.velikov@xxxxxxxxx>
---
drivers/gpu/drm/drm_auth.c | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c
index 232abbba3686..c6bf52c310a9 100644
--- a/drivers/gpu/drm/drm_auth.c
+++ b/drivers/gpu/drm/drm_auth.c
@@ -61,6 +61,8 @@
* trusted clients.
*/
+static bool drm_is_current_master_locked(struct drm_file *fpriv);
A bit a bikeshed, but we try to avoid forward declarations when they're
not needed. If you don't want to tear apart drm_is_current_master and the
_locked version then just move them together.
Can you pls do that and respin?
Otherwise looks all great.
-Daniel
Yeah, I was trying to keep the logic in _locked close to
drm_is_current_master. But got it, will do.
