From: Jesper Juhl Subject: Re: [PATCH] NFS: nfsaclsvc_encode_getaclres() - Fix potential NULL deref and tiny optimization. Date: Sat, 28 Oct 2006 00:01:48 +0200 Message-ID: <200610280001.49272.jesper.juhl@gmail.com> References: <200610272316.47089.jesper.juhl@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: Andrew Morton , Jesper Juhl , linux-kernel@vger.kernel.org, Neil Brown , nfs@lists.sourceforge.net, Andreas Gruenbacher Return-path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.92] helo=mail.sourceforge.net) by sc8-sf-list2-new.sourceforge.net with esmtp (Exim 4.43) id 1GdZkL-0003IQ-EB for nfs@lists.sourceforge.net; Fri, 27 Oct 2006 15:00:13 -0700 Received: from nf-out-0910.google.com ([64.233.182.190]) by mail.sourceforge.net with esmtp (Exim 4.44) id 1GdZkM-0001oR-89 for nfs@lists.sourceforge.net; Fri, 27 Oct 2006 15:00:14 -0700 Received: by nf-out-0910.google.com with SMTP id p46so2087382nfa for ; Fri, 27 Oct 2006 15:00:12 -0700 (PDT) To: David Rientjes In-Reply-To: List-Id: "Discussion of NFS under Linux development, interoperability, and testing." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: nfs-bounces@lists.sourceforge.net Errors-To: nfs-bounces@lists.sourceforge.net On Friday 27 October 2006 23:46, David Rientjes wrote: > On Fri, 27 Oct 2006, Jesper Juhl wrote: > > > In fs/nfsd/nfs2acl.c::nfsaclsvc_encode_getaclres() I see a few issues. > > > > 1) At the top of the function we assign to the 'inode' variable by > > dereferencing 'dentry', but further down we test 'dentry' for NULL. So, if > > 'dentry' (which is really 'resp->fh.fh_dentry') can be NULL, then either > > we have a potential NULL pointer deref bug or we have a superflous test. > > > > resp->fh.fh_dentry cannot be NULL on nfsaclsvc_encode_getaclres so the > early assignment is appropriate for both *dentry and *inode. I didn't convince myself of that on my first scan of the code, that's why I opted to keep the NULL check. > *inode will > need to be checked for NULL in the conditional, however, and return 0 on > true. > Right, that agrees with my reading as well. > > 3) There are two locations in the function where we may return before we > > use the value of the variable 'w', but we compute it at the very top of the > > function. So in the case where we return early we have wasted a few cycles > > computing a value that was never used. > > > > w should be an unsigned int. > Makes sense. Thank you for commenting. Here's a patch, on top of the previous one, to address you comments. Feedback welcome. Signed-off-by: Jesper Juhl --- fs/nfsd/nfs2acl.c | 7 +++---- 1 files changed, 3 insertions(+), 4 deletions(-) diff --git a/fs/nfsd/nfs2acl.c b/fs/nfsd/nfs2acl.c index d89d63f..069d7d0 100644 --- a/fs/nfsd/nfs2acl.c +++ b/fs/nfsd/nfs2acl.c @@ -222,14 +222,13 @@ static int nfsaclsvc_encode_getaclres(st { struct dentry *dentry = resp->fh.fh_dentry; struct kvec *head = rqstp->rq_res.head; - struct inode *inode; + struct inode *inode = dentry->d_inode; unsigned int base; - int w; + unsigned int w; int n; - if (dentry == NULL || dentry->d_inode == NULL) + if (!inode) return 0; - inode = dentry->d_inode; p = nfs2svc_encode_fattr(rqstp, p, &resp->fh); *p++ = htonl(resp->mask); ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ NFS maillist - NFS@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/nfs