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authorDesmond Cheong Zhi Xi <desmondcheongzx@gmail.com>2021-06-20 19:03:26 +0800
committerDaniel Vetter <daniel.vetter@ffwll.ch>2021-06-21 17:42:28 +0200
commit1815d9c86e3090477fbde066ff314a7e9721ee0f (patch)
treeb8b020baa41abd8fe9f046745ed84fbeaeb26984 /drivers/gpu
parente541845ae0858616c52dd97df4bf91568c7a7a1b (diff)
drm: add a locked version of drm_is_current_master
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> Cc: stable@vger.kernel.org Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20210620110327.4964-2-desmondcheongzx@gmail.com
Diffstat (limited to 'drivers/gpu')
-rw-r--r--drivers/gpu/drm/drm_auth.c51
1 files changed, 32 insertions, 19 deletions
diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c
index 232abbba3686..86d4b72e95cb 100644
--- a/drivers/gpu/drm/drm_auth.c
+++ b/drivers/gpu/drm/drm_auth.c
@@ -61,6 +61,35 @@
* trusted clients.
*/
+static bool drm_is_current_master_locked(struct drm_file *fpriv)
+{
+ lockdep_assert_held_once(&fpriv->master->dev->master_mutex);
+
+ return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master;
+}
+
+/**
+ * drm_is_current_master - checks whether @priv is the current master
+ * @fpriv: DRM file private
+ *
+ * Checks whether @fpriv is current master on its device. This decides whether a
+ * client is allowed to run DRM_MASTER IOCTLs.
+ *
+ * Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting
+ * - the current master is assumed to own the non-shareable display hardware.
+ */
+bool drm_is_current_master(struct drm_file *fpriv)
+{
+ bool ret;
+
+ mutex_lock(&fpriv->master->dev->master_mutex);
+ ret = drm_is_current_master_locked(fpriv);
+ mutex_unlock(&fpriv->master->dev->master_mutex);
+
+ return ret;
+}
+EXPORT_SYMBOL(drm_is_current_master);
+
int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv)
{
struct drm_auth *auth = data;
@@ -223,7 +252,7 @@ int drm_setmaster_ioctl(struct drm_device *dev, void *data,
if (ret)
goto out_unlock;
- if (drm_is_current_master(file_priv))
+ if (drm_is_current_master_locked(file_priv))
goto out_unlock;
if (dev->master) {
@@ -272,7 +301,7 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data,
if (ret)
goto out_unlock;
- if (!drm_is_current_master(file_priv)) {
+ if (!drm_is_current_master_locked(file_priv)) {
ret = -EINVAL;
goto out_unlock;
}
@@ -321,7 +350,7 @@ void drm_master_release(struct drm_file *file_priv)
if (file_priv->magic)
idr_remove(&file_priv->master->magic_map, file_priv->magic);
- if (!drm_is_current_master(file_priv))
+ if (!drm_is_current_master_locked(file_priv))
goto out;
drm_legacy_lock_master_cleanup(dev, master);
@@ -343,22 +372,6 @@ out:
}
/**
- * drm_is_current_master - checks whether @priv is the current master
- * @fpriv: DRM file private
- *
- * Checks whether @fpriv is current master on its device. This decides whether a
- * client is allowed to run DRM_MASTER IOCTLs.
- *
- * Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting
- * - the current master is assumed to own the non-shareable display hardware.
- */
-bool drm_is_current_master(struct drm_file *fpriv)
-{
- return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master;
-}
-EXPORT_SYMBOL(drm_is_current_master);
-
-/**
* drm_master_get - reference a master pointer
* @master: &struct drm_master
*