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drm: Fix authentication kernel crash

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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 <thellstrom@vmware.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Thomas Hellstrom
2012-01-24 18:54:21 +01:00
committed by Dave Airlie
parent 15b63d3526
commit 598781d711
3 changed files with 11 additions and 1 deletions
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5
drivers/gpu/drm/drm_fops.c
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@@ -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);