Re: [PATCH 6/5]: XFS: Prevent use-after-free caused by synchronous inode reclaim

Dave Chinner
2008-10-09T08:06:38Z

On Thu, Oct 09, 2008 at 03:02:45AM -0400, Christoph Hellwig wrote:
> On Thu, Oct 09, 2008 at 03:21:34PM +1100, Dave Chinner wrote:
> > Folks,
> >
> > The following patch fixes a use after free I just found.
> > It appears that switching between SLAB and SLUB seems to
> > turn off slab/slub memory poisoning, so i d??dn't realise
> > I'd be running for some time without poisoning turned on.
> > Once I turned poisoning back on I found this use-after-free
> > immediately on the first unmount trying to reclaim a clean
> > realtime bitmap inode.
> >
> > With this patch, the netire patchset that I posted yesterday
> > passes xfsqa with memory poisoning turned on.
>
> Looks good.
>
> > + XFS_STATS_INC(vn_reclaim);
> > + if (xfs_reclaim(ip))
> > + panic("%s: cannot reclaim 0x%p\n", __func__, inode);
>
> Eventually we should kill the return value from xfs_reclaim and just put
> an assert directly into it. In fact given that xfs_reclaim is quite
> OS dependent we might just merge the content directly into
> destroy_inode.

Yeah, I was thinking of doing exactly that in this patch, but I
figured that I'd just do the minimum needed to fix the bug because
we're getting close to the next merge window.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com