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Subject[08/65] drm: Fix authentication kernel crash
3.0-stable review patch.  If anyone has any objections, please let me know.


From: Thomas Hellstrom <>

commit 598781d71119827b454fd75d46f84755bca6f0c6 upstream.

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 <>
Reviewed-by: Daniel Vetter <>
Signed-off-by: Dave Airlie <>
Signed-off-by: Greg Kroah-Hartman <>

drivers/gpu/drm/drm_auth.c | 6 +++++-
drivers/gpu/drm/drm_fops.c | 5 +++++
include/drm/drmP.h | 1 +
3 files changed, 11 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/drm_auth.c
+++ b/drivers/gpu/drm/drm_auth.c
@@ -101,7 +101,7 @@ static int drm_add_magic(struct drm_mast
* Searches and unlinks the entry in drm_device::magiclist with the magic
* number hash key, while holding the drm_device::struct_mutex lock.
-static int drm_remove_magic(struct drm_master *master, drm_magic_t magic)
+int drm_remove_magic(struct drm_master *master, drm_magic_t magic)
struct drm_magic_entry *pt;
struct drm_hash_item *hash;
@@ -136,6 +136,8 @@ static int drm_remove_magic(struct drm_m
* If there is a magic number in drm_file::magic then use it, otherwise
* searches an unique non-zero magic number and add it associating it with \p
* file_priv.
+ * This ioctl needs protection by the drm_global_mutex, which protects
+ * struct drm_file::magic and struct drm_magic_entry::priv.
int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv)
@@ -173,6 +175,8 @@ int drm_getmagic(struct drm_device *dev,
* \return zero if authentication successed, or a negative number otherwise.
* Checks if \p file_priv is associated with the magic number passed in \arg.
+ * This ioctl needs protection by the drm_global_mutex, which protects
+ * struct drm_file::magic and struct drm_magic_entry::priv.
int drm_authmagic(struct drm_device *dev, void *data,
struct drm_file *file_priv)
--- a/drivers/gpu/drm/drm_fops.c
+++ b/drivers/gpu/drm/drm_fops.c
@@ -486,6 +486,11 @@ int drm_release(struct inode *inode, str

+ /* Release any auth tokens that might point to this file_priv,
+ (do that under the drm_global_mutex) */
+ if (file_priv->magic)
+ (void) drm_remove_magic(file_priv->master, file_priv->magic);
/* if the master has gone away we can't do anything with the lock */
if (file_priv->minor->master)
drm_master_release(dev, filp);
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1323,6 +1323,7 @@ extern int drm_getmagic(struct drm_devic
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);

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