From: Frank Filz Subject: [PATCH] nfs: Fix NFS v4 client handling of MAY_EXEC in nfs_permission. Date: Mon, 18 May 2009 12:29:43 -0700 Message-ID: <1242674983.4273.8.camel@dyn9047022153> Mime-Version: 1.0 Content-Type: text/plain Cc: Eugene Teo , security@kernel.org, Trond Myklebust , Bruce Fields To: NFS List , NFS V4 Mailing List , Linux Kernel Mailing List Return-path: Received: from e9.ny.us.ibm.com ([32.97.182.139]:43853 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751396AbZERT3o (ORCPT ); Mon, 18 May 2009 15:29:44 -0400 Sender: linux-nfs-owner@vger.kernel.org List-ID: Sorry for the resend, got lkml address wrong... The problem is that permission checking is skipped if atomic open is possible, but when exec opens a file, it just opens it O_READONLY which means EXEC permission will not be checked at that time. This problem is observed by the following sequence (executed as root): mount -t nfs4 server:/ /mnt4 echo "ls" >/mnt4/foo chmod 744 /mnt4/foo su guest -c "mnt4/foo" Signed-off-by: Frank Filz --- fs/nfs/dir.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index 370b190..89f98e9 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -1943,7 +1943,8 @@ int nfs_permission(struct inode *inode, int mask) case S_IFREG: /* NFSv4 has atomic_open... */ if (nfs_server_capable(inode, NFS_CAP_ATOMIC_OPEN) - && (mask & MAY_OPEN)) + && (mask & MAY_OPEN) + && !(mask & MAY_EXEC)) goto out; break; case S_IFDIR: