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Commit 598781d7 authored by Thomas Hellstrom's avatar Thomas Hellstrom Committed by Dave Airlie
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drm: Fix authentication kernel crash 



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: default avatarThomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
parent 15b63d35

drivers/gpu/drm/drm_auth.c

+5 −1
Original line number Diff line number Diff line
@@ -101,7 +101,7 @@ static int drm_add_magic(struct drm_master *master, struct drm_file *priv, 
 * 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_master *master, drm_magic_t magic) 
 * 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, void *data, struct drm_file *file_priv) 
 * \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)

drivers/gpu/drm/drm_fops.c

+5 −0
Original line number Diff line number Diff line
@@ -487,6 +487,11 @@ int drm_release(struct inode *inode, struct file *filp) 
		  (long)old_encode_dev(file_priv->minor->device),

		  dev->open_count);



	/* 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);

include/drm/drmP.h

+1 −0
Original line number Diff line number Diff line
@@ -1328,6 +1328,7 @@ extern int drm_getmagic(struct drm_device *dev, void *data, 
			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);