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Commit fd649f10 authored by Nikolay Borisov's avatar Nikolay Borisov Committed by David Sterba
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btrfs: Fix use-after-free when cleaning up fs_devs with a single stale device 



Commit 4fde46f0 ("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: 4fde46f0 ("Btrfs: free the stale device")
Signed-off-by: default avatarNikolay Borisov <nborisov@suse.com>
Reviewed-by: default avatarAnand Jain <anand.jain@oracle.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 627e0873

fs/btrfs/volumes.c

+1 −0
Original line number Diff line number Diff line
@@ -645,6 +645,7 @@ static void btrfs_free_stale_devices(const char *path, 
				btrfs_sysfs_remove_fsid(fs_devs);

				list_del(&fs_devs->list);

				free_fs_devices(fs_devs);

				break;

			} else {

				fs_devs->num_devices--;

				list_del(&dev->dev_list);