Patch "autofs: revert "autofs: fix AT_NO_AUTOMOUNT not being honored"" has been added to the 4.14-stable tree

[<gregkh@linuxfoundation.org>]

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

    autofs: revert "autofs: fix AT_NO_AUTOMOUNT not being honored"

to the 4.14-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:
     autofs-revert-autofs-fix-at_no_automount-not-being-honored.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 5d38f049cee1e1c4a7ac55aa79d37d01ddcc3860 Mon Sep 17 00:00:00 2001
From: Ian Kent <raven@themaw.net>
Date: Wed, 29 Nov 2017 16:11:26 -0800
Subject: autofs: revert "autofs: fix AT_NO_AUTOMOUNT not being honored"

From: Ian Kent <raven@themaw.net>

commit 5d38f049cee1e1c4a7ac55aa79d37d01ddcc3860 upstream.

Commit 42f461482178 ("autofs: fix AT_NO_AUTOMOUNT not being honored")
allowed the fstatat(2) system call to properly honor the AT_NO_AUTOMOUNT
flag but introduced a semantic change.

In order to honor AT_NO_AUTOMOUNT a semantic change was made to the
negative dentry case for stat family system calls in follow_automount().

This changed the unconditional triggering of an automount in this case
to no longer be done and an error returned instead.

This has caused more problems than I expected so reverting the change is
needed.

In a discussion with Neil Brown it was concluded that the automount(8)
daemon can implement this change without kernel modifications.  So that
will be done instead and the autofs module documentation updated with a
description of the problem and what needs to be done by module users for
this specific case.

Link: http://lkml.kernel.org/r/151174730120.6162.3848002191530283984.stgit@pluto.themaw.net
Fixes: 42f4614821 ("autofs: fix AT_NO_AUTOMOUNT not being honored")
Signed-off-by: Ian Kent <raven@themaw.net>
Cc: Neil Brown <neilb@suse.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: Colin Walters <walters@redhat.com>
Cc: Ondrej Holy <oholy@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/namei.c         |   15 +++------------
 include/linux/fs.h |    3 ++-
 2 files changed, 5 insertions(+), 13 deletions(-)

--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1129,18 +1129,9 @@ static int follow_automount(struct path
 	 * of the daemon to instantiate them before they can be used.
 	 */
 	if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
-			   LOOKUP_OPEN | LOOKUP_CREATE |
-			   LOOKUP_AUTOMOUNT))) {
-		/* Positive dentry that isn't meant to trigger an
-		 * automount, EISDIR will allow it to be used,
-		 * otherwise there's no mount here "now" so return
-		 * ENOENT.
-		 */
-		if (path->dentry->d_inode)
-			return -EISDIR;
-		else
-			return -ENOENT;
-	}
+			   LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
+	    path->dentry->d_inode)
+		return -EISDIR;
 
 	if (path->dentry->d_sb->s_user_ns != &init_user_ns)
 		return -EACCES;
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3069,7 +3069,8 @@ static inline int vfs_lstat(const char _
 static inline int vfs_fstatat(int dfd, const char __user *filename,
 			      struct kstat *stat, int flags)
 {
-	return vfs_statx(dfd, filename, flags, stat, STATX_BASIC_STATS);
+	return vfs_statx(dfd, filename, flags | AT_NO_AUTOMOUNT,
+			 stat, STATX_BASIC_STATS);
 }
 static inline int vfs_fstat(int fd, struct kstat *stat)
 {


Patches currently in stable-queue which might be from raven@themaw.net are

queue-4.14/autofs-revert-autofs-fix-at_no_automount-not-being-honored.patch
queue-4.14/autofs-revert-autofs-take-more-care-to-not-update-last_used-on-path-walk.patch