From: Lingkai Dong Lingkai.Dong@arm.com
The DRM subsystem keeps a record of the owner of a DRM device file descriptor using thread group ID (TGID) instead of process ID (PID), to ensures all threads within the same userspace process are considered the owner. However, the DRM master ownership check compares the current thread's PID against the record, so the thread is incorrectly considered to be not the FD owner if the PID is not equal to the TGID. This causes DRM ioctls to be denied master privileges, even if the same thread that opened the FD performs an ioctl. Fix this by checking TGID.
Fixes: 4230cea89cafb ("drm: Track clients by tgid and not tid") Signed-off-by: Lingkai Dong lingkai.dong@arm.com Reviewed-by: Christian König christian.koenig@amd.com Reviewed-by: Tvrtko Ursulin tvrtko.ursulin@intel.com Cc: stable@vger.kernel.org # v6.4+ Link: https://patchwork.freedesktop.org/patch/msgid/PA6PR08MB107665920BE9A96658CDA... Signed-off-by: Christian König christian.koenig@amd.com (cherry picked from commit 5a6c9a05e55cb2972396cc991af9d74c8c15029a) --- drivers/gpu/drm/drm_auth.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index cf92a9ae8034c..7ef8a2762e818 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -235,7 +235,7 @@ static int drm_new_set_master(struct drm_device *dev, struct drm_file *fpriv) static int drm_master_check_perm(struct drm_device *dev, struct drm_file *file_priv) { - if (file_priv->pid == task_pid(current) && file_priv->was_master) + if (file_priv->pid == task_tgid(current) && file_priv->was_master) return 0;
if (!capable(CAP_SYS_ADMIN))