Re: [PATCH 1/2] xfs: don't allow UAF in xlog_recover_iget

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, Mar 20, 2026 at 12:19:19AM -0700, Christoph Hellwig wrote:
> "Don't allow UAF" reads rally giberrish.
> 
> On Thu, Mar 19, 2026 at 10:09:38AM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <djwong@kernel.org>
> > 
> > Fix this function to avoid touching the passed in ipp argument until
> > we're 100% certain that we're returning zero.  This avoids creating a
> > dangling pointer in the caller.
> 
> Why does this matter?  The caller need to check the return value.

I think the fundamental problem here is that Long Li ran a static
checker, and the static checker suggested that the callsite in
xfs_attri_recover_work should be fixed by guarding the xfs_irele call in
the error handler with a null pointer check.  That's completely wrong,
the xfs_irele should never have been put in the error path at all.

So the proper fix is the one in the next patch that removes the
xfs_irele.  At the same time, xlog_recover_iget should get fixed so that
it never exposes stale pointers in the first place.

"Fix this function to avoid exposing a stale pointer to the caller when
returning an error code after dqattach fails." ?

> > The xfs_irele call in
> > xfs_attri_recover_work was never correct and should go away.
> 
> No idea what this is supposed to say, seem unrelated to this patch.

Yeah, I'll just drop that.

--D