Re: [PATCH] Fix use after free when closing log/rt devices

[Mark Goodwin <markgw@sgi.com>]

Christoph Hellwig wrote:
> On Fri, Jun 27, 2008 at 03:14:46PM +1000, Lachlan McIlroy wrote:
>> The call to xfs_free_buftarg() will free the memory used by it's argument
>> so we need to save the bdev to pass to xfs_blkdev_put()
>>
>> Lachlan
>>
>> --- fs/xfs/linux-2.6/xfs_super.c_1.432	2008-06-27 14:51:17.000000000 +1000
>> +++ fs/xfs/linux-2.6/xfs_super.c	2008-06-27 14:59:26.000000000 +1000
>> @@ -781,13 +781,17 @@ STATIC void
>> xfs_close_devices(
>> 	struct xfs_mount	*mp)
>> {
>> +	struct block_device	*bdev;
>> +
>> 	if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp) {
>> +		bdev = mp->m_logdev_targp->bt_bdev;
>> 		xfs_free_buftarg(mp->m_logdev_targp);
>> -		xfs_blkdev_put(mp->m_logdev_targp->bt_bdev);
>> +		xfs_blkdev_put(bdev);
>> 	}
>> 	if (mp->m_rtdev_targp) {
>> +		bdev = mp->m_rtdev_targp->bt_bdev;
>> 		xfs_free_buftarg(mp->m_rtdev_targp);
>> -		xfs_blkdev_put(mp->m_rtdev_targp->bt_bdev);
>> +		xfs_blkdev_put(bdev);
>> 	}
> 
> Looks good, alhough two local variables inside the ifs might be cleaner:
> 
> 	if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp) {
> 		struct block_device *logdev = mp->m_logdev_targp->bt_bdev;
> 
> 		xfs_free_buftarg(mp->m_logdev_targp);
> 		xfs_blkdev_put(logdev);
> 	}
> 
> 	...

do we have any QA tests that test external log?

-- Mark