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@ffwll.ch Signed-off-by: Desmond Cheong Zhi Xi desmondcheongzx@gmail.com Reviewed-by: Emil Velikov emil.l.velikov@gmail.com
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.