Patch "should_follow_link(): validate ->d_seq after having decided to follow" has been added to the 4.4-stable tree

Patch "should_follow_link(): validate ->d_seq after having decided to follow" has been added to the 4.4-stable tree

[gregkh]

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

    should_follow_link(): validate ->d_seq after having decided to follow

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:
     should_follow_link-validate-d_seq-after-having-decided-to-follow.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 <stable@vger.kernel.org> know about it.


>From a7f775428b8f5808815c0e3004020cedb94cbe3b Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sat, 27 Feb 2016 19:31:01 -0500
Subject: should_follow_link(): validate ->d_seq after having decided to follow

From: Al Viro <viro@zeniv.linux.org.uk>

commit a7f775428b8f5808815c0e3004020cedb94cbe3b upstream.

... otherwise d_is_symlink() above might have nothing to do with
the inode value we've got.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/namei.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1711,6 +1711,11 @@ static inline int should_follow_link(str
 		return 0;
 	if (!follow)
 		return 0;
+	/* make sure that d_is_symlink above matches inode */
+	if (nd->flags & LOOKUP_RCU) {
+		if (read_seqcount_retry(&link->dentry->d_seq, seq))
+			return -ECHILD;
+	}
 	return pick_link(nd, link, inode, seq);
 }
 


Patches currently in stable-queue which might be from viro@zeniv.linux.org.uk are

queue-4.4/make-sure-that-freeing-shmem-fast-symlinks-is-rcu-delayed.patch
queue-4.4/do_last-eloop-failure-exit-should-be-done-after-leaving-rcu-mode.patch
queue-4.4/bcache-fix-a-leak-in-bch_cached_dev_run.patch
queue-4.4/do_last-don-t-let-a-bogus-return-value-from-open-et.al.-to-confuse-us.patch
queue-4.4/locks-fix-unlock-when-fcntl_setlk-races-with-a-close.patch
queue-4.4/namei-d_inode-of-a-pinned-dentry-is-stable-only-for-positives.patch
queue-4.4/should_follow_link-validate-d_seq-after-having-decided-to-follow.patch
queue-4.4/uml-fix-hostfs-mknod.patch
queue-4.4/hpfs-don-t-truncate-the-file-when-delete-fails.patch