Re: [PATCH] nfsd: fix oops on mixed NFSv4/NFSv3 client access

[Bruce Fields <bfields@fieldses.org>]

On Wed, Aug 05, 2020 at 03:17:54PM -0400, Chuck Lever wrote:
> Hi Bruce-
> 
> > On Aug 5, 2020, at 3:10 PM, bfields@fieldses.org wrote:
> > 
> > From: "J. Bruce Fields" <bfields@redhat.com>
> > 
> > If an NFSv2/v3 client breaks an NFSv4 client's delegation, it will hit a
> > NULL dereference in nfsd_breaker_owns_lease().
> > 
> > Easily reproduceable with for example
> > 
> > 	mount -overs=4.2 server:/export /mnt/
> > 	sleep 1h </mnt/file &
> > 	mount -overs=3 server:/export /mnt2/
> > 	touch /mnt2/file
> > 
> > Reported-by: Robert Dinse <nanook@eskimo.com>
> > Fixes: 28df3d1539de50 ("nfsd: clients don't need to break their own delegations")
> 
> May I add
> 
> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=208807
> 
> And send this in the first NFSD v5.9 -rc pull request?

Sounds good, thanks!

--b.

> 
> 
> > Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> > ---
> > fs/nfsd/nfs4state.c | 2 ++
> > 1 file changed, 2 insertions(+)
> > 
> > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > index 9fc0a1b9e4dd..45f3832d70d4 100644
> > --- a/fs/nfsd/nfs4state.c
> > +++ b/fs/nfsd/nfs4state.c
> > @@ -4597,6 +4597,8 @@ static bool nfsd_breaker_owns_lease(struct file_lock *fl)
> > 	if (!i_am_nfsd())
> > 		return NULL;
> > 	rqst = kthread_data(current);
> > +	if (!rqst->rq_lease_breaker)
> > +		return NULL;
> > 	clp = *(rqst->rq_lease_breaker);
> > 	return dl->dl_stid.sc_client == clp;
> > }
> > -- 
> > 2.26.2
> > 
> 
> --
> Chuck Lever
> 
>