Patch "NFS: Ensure we revalidate attributes before using execute_ok()" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

NFS: Ensure we revalidate attributes before using execute_ok()

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
nfs-ensure-we-revalidate-attributes-before-using-execute_ok.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Trond Myklebust <[email protected]>
Date: Mon, 28 Dec 2015 19:30:05 -0500
Subject: NFS: Ensure we revalidate attributes before using execute_ok()

From: Trond Myklebust <[email protected]>

commit 5c5fc09a1157a11dbe84e6421c3e0b37d05238cb upstream.

Donald Buczek reports that NFS clients can also report incorrect results for access() due to lack of revalidation of attributes before calling execute_ok().
Looking closely, it seems chdir() is afflicted with the same problem.

Fix is to ensure we call nfs_revalidate_inode_rcu() or nfs_revalidate_inode() as appropriate before deciding to trust execute_ok().

---
 fs/nfs/dir.c |   18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

@@ -2421,6 +2421,20 @@ int nfs_may_open(struct inode *inode, st
 }
 EXPORT_SYMBOL_GPL(nfs_may_open);
 
+static int nfs_execute_ok(struct inode *inode, int mask)
+{
+	struct nfs_server *server = NFS_SERVER(inode);
+	int ret;
+
+	if (mask & MAY_NOT_BLOCK)
+		ret = nfs_revalidate_inode_rcu(server, inode);
+	else
+		ret = nfs_revalidate_inode(server, inode);
+	if (ret == 0 && !execute_ok(inode))
+		ret = -EACCES;
+	return ret;
+}
+
 int nfs_permission(struct inode *inode, int mask)
 {
 	struct rpc_cred *cred;

@@ -2470,8 +2484,8 @@ force_lookup:
 			res = PTR_ERR(cred);
 	}
 out:
-	if (!res && (mask & MAY_EXEC) && !execute_ok(inode))
-		res = -EACCES;
+	if (!res && (mask & MAY_EXEC))
+		res = nfs_execute_ok(inode, mask);
 
 	dfprintk(VFS, "NFS: permission(%s/%lu), mask=0x%x, res=%d\n",
 		inode->i_sb->s_id, inode->i_ino, mask, res);

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/nfsd-fix-up-the-supattr_exclcreat-attributes.patch queue-4.4/nfsv4-don-t-perform-cached-access-checks-before-we-ve-opened-the-file.patch queue-4.4/nfs-ensure-we-revalidate-attributes-before-using-execute_ok.patch