[patch 21/87] nfs: Fix NFS v4 client handling of MAY_EXEC in nfs_permission.

[Greg KH]

2.6.29-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Frank Filz <ffilzlnx@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
Tested-by: Eugene Teo <eugeneteo@xxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 fs/nfs/dir.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1943,7 +1943,8 @@ int nfs_permission(struct inode *inode, 
 		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:


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