[3.16.y-ckt stable] Patch "do_last(): don't let a bogus return value from ->open() et.al. to confuse us" has been added to the 3.16.y-ckt tree

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    do_last(): don't let a bogus return value from ->open() et.al. to confuse us

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt26.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

---8<------------------------------------------------------------

>From 9ecd5948cf0ada80125ffd89859c12a469b3d058 Mon Sep 17 00:00:00 2001
From: Al Viro <viro at zeniv.linux.org.uk>
Date: Sat, 27 Feb 2016 19:17:33 -0500
Subject: do_last(): don't let a bogus return value from ->open() et.al. to
 confuse us

commit c80567c82ae4814a41287618e315a60ecf513be6 upstream.

... into returning a positive to path_openat(), which would interpret that
as "symlink had been encountered" and proceed to corrupt memory, etc.
It can only happen due to a bug in some ->open() instance or in some LSM
hook, etc., so we report any such event *and* make sure it doesn't trick
us into further unpleasantness.

Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/namei.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/namei.c b/fs/namei.c
index 8a0c3d9d8298..34f8224be4ed 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3108,6 +3108,10 @@ opened:
 			goto exit_fput;
 	}
 out:
+	if (unlikely(error > 0)) {
+		WARN_ON(1);
+		error = -EINVAL;
+	}
 	if (got_write)
 		mnt_drop_write(nd->path.mnt);
 	path_put(&save_parent);