nfs: Fix NFS v4 client handling of MAY_EXEC in nfs_permission.

commit 7ee2cb7f32b299c2b06a31fde155457203e4b7dd upstream.

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 <ffilzlnx@us.ibm.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Tested-by: Eugene Teo <eugeneteo@kernel.sg>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 3b2f6973e7c50cbfdd579351ae99ba5e746bc64d..5dd75c00ebf43fed8c2e16244b6f8d57ffb9f87b 100644 (file)
--- 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: