Messages in this thread Patch in this message | | | 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 |
| |
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 <jesper.juhl@gmail.com> ---
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); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |