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btrfs: Fix use-after-free when cleaning up fs_devs with a single stale device
authorNikolay Borisov <nborisov@suse.com>
Tue, 30 Jan 2018 14:07:37 +0000 (16:07 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 22 Mar 2018 08:23:32 +0000 (09:23 +0100)
commite1994e4d56b36d5d4cc9aacd252e3fd60d3c5595
treea63fd878c9809700256187abdcffc60acb63cd3a
parent97c3e46ef53748278286fc09dcc30b138d6677c4
btrfs: Fix use-after-free when cleaning up fs_devs with a single stale device

commit fd649f10c3d21ee9d7542c609f29978bdf73ab94 upstream.

Commit 4fde46f0cc71 ("Btrfs: free the stale device") introduced
btrfs_free_stale_device which iterates the device lists for all
registered btrfs filesystems and deletes those devices which aren't
mounted. In a btrfs_devices structure has only 1 device attached to it
and it is unused then btrfs_free_stale_devices will proceed to also free
the btrfs_fs_devices struct itself. Currently this leads to a use after
free since list_for_each_entry will try to perform a check on the
already freed memory to see if it has to terminate the loop.

The fix is to use 'break' when we know we are freeing the current
fs_devs.

Fixes: 4fde46f0cc71 ("Btrfs: free the stale device")
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
fs/btrfs/volumes.c