linux-kernel - Re: [PATCH] nfsd: fix NULL dereference in nfsd

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Date:	Fri, 20 Aug 2010 17:29:58 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Takashi Iwai <tiwai@...e.de>
Cc:	Neil Brown <neilb@...e.de>, Al Viro <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@....de>, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nfsd: fix NULL dereference in nfsd_statfs()

On Sat, Aug 14, 2010 at 09:02:35AM -0400, J. Bruce Fields wrote:
> On Fri, Aug 13, 2010 at 03:53:49PM +0200, Takashi Iwai wrote:
> > The commit ebabe9a9001af0af56c0c2780ca1576246e7a74b
> >     pass a struct path to vfs_statfs
> > introduced the struct path initialization, and this seems to trigger
> > an Oops on my machine.
> > 
> > fh_dentry field may be NULL and set later in fh_verify(), thus the
> > initialization of path must be after fh_verify().
> > 
> > Signed-off-by: Takashi Iwai <tiwai@...e.de>
> 
> I'm travelling, but, looks good:
> 
> 	Acked-by: J. Bruce Fields <bfields@...hat.com>

Sorry for the delay, queued up to send to Linus for 2.6.36 soon.

--b.

> 
> --b.
> 
> > ---
> >  fs/nfsd/vfs.c |   14 ++++++++------
> >  1 files changed, 8 insertions(+), 6 deletions(-)
> > 
> > diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> > index 96360a8..661a6cf 100644
> > --- a/fs/nfsd/vfs.c
> > +++ b/fs/nfsd/vfs.c
> > @@ -2033,15 +2033,17 @@ out:
> >  __be32
> >  nfsd_statfs(struct svc_rqst *rqstp, struct svc_fh *fhp, struct kstatfs *stat, int access)
> >  {
> > -	struct path path = {
> > -		.mnt	= fhp->fh_export->ex_path.mnt,
> > -		.dentry	= fhp->fh_dentry,
> > -	};
> >  	__be32 err;
> >  
> >  	err = fh_verify(rqstp, fhp, 0, NFSD_MAY_NOP | access);
> > -	if (!err && vfs_statfs(&path, stat))
> > -		err = nfserr_io;
> > +	if (!err) {
> > +		struct path path = {
> > +			.mnt	= fhp->fh_export->ex_path.mnt,
> > +			.dentry	= fhp->fh_dentry,
> > +		};
> > +		if (vfs_statfs(&path, stat))
> > +			err = nfserr_io;
> > +	}
> >  	return err;
> >  }
> >  
> > -- 
> > 1.7.2.1
> > 
--
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