From mboxrd@z Thu Jan 1 00:00:00 1970 From: "J. Bruce Fields" Subject: Re: [PATCH] NFSD: Don't hold unrefcounted creds over call to nfsd_setuser() Date: Thu, 2 Jul 2009 16:39:37 -0400 Message-ID: <20090702203937.GA10504@fieldses.org> References: <20090702133532.28297.89635.stgit@warthog.procyon.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: steved@redhat.com, rasmus-tUP8e6pgWdNlY7y4Fx5NiA@public.gmane.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org To: David Howells Return-path: Received: from 174-143-236-118.static.slicehost.net ([174.143.236.118]:36521 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753952AbZGBUji (ORCPT ); Thu, 2 Jul 2009 16:39:38 -0400 In-Reply-To: <20090702133532.28297.89635.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Thu, Jul 02, 2009 at 02:35:32PM +0100, David Howells wrote: > nfsd_open() gets an unrefcounted pointer to the current process's effective > credentials at the top of the function, then calls nfsd_setuser() via > fh_verify() - which may replace and destroy the current process's effective > credentials - and then passes the unrefcounted pointer to dentry_open() - but > the credentials may have been destroyed by this point. > > Instead, the value from current_cred() should be passed directly to > dentry_open() as one of its arguments, rather than being cached in a variable. Got it, thanks. How easy is it to hit this case? (Just wondering whether to submit for stable.) --b. > > Possibly fh_verify() should return the creds to use. > > Signed-off-by: David Howells > --- > > fs/nfsd/vfs.c | 3 +-- > 1 files changed, 1 insertions(+), 2 deletions(-) > > > diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c > index 4145083..23341c1 100644 > --- a/fs/nfsd/vfs.c > +++ b/fs/nfsd/vfs.c > @@ -678,7 +678,6 @@ __be32 > nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, > int access, struct file **filp) > { > - const struct cred *cred = current_cred(); > struct dentry *dentry; > struct inode *inode; > int flags = O_RDONLY|O_LARGEFILE; > @@ -733,7 +732,7 @@ nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, > vfs_dq_init(inode); > } > *filp = dentry_open(dget(dentry), mntget(fhp->fh_export->ex_path.mnt), > - flags, cred); > + flags, current_cred()); > if (IS_ERR(*filp)) > host_err = PTR_ERR(*filp); > else >