[3.16.y-ckt stable] Patch "cifs_dbg() outputs an uninitialized buffer in cifs_readdir()" 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

    cifs_dbg() outputs an uninitialized buffer in cifs_readdir()

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-ckt24.

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 c9c482ef696a6eefe7f8d25e140593441f948cb2 Mon Sep 17 00:00:00 2001
From: Vasily Averin <vvs at virtuozzo.com>
Date: Thu, 14 Jan 2016 13:41:14 +0300
Subject: cifs_dbg() outputs an uninitialized buffer in cifs_readdir()

commit 01b9b0b28626db4a47d7f48744d70abca9914ef1 upstream.

In some cases tmp_bug can be not filled in cifs_filldir and stay uninitialized,
therefore its printk with "%s" modifier can leak content of kernelspace memory.
If old content of this buffer does not contain '\0' access bejond end of
allocated object can crash the host.

Signed-off-by: Vasily Averin <vvs at virtuozzo.com>
Signed-off-by: Steve French <sfrench at localhost.localdomain>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/cifs/readdir.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c
index b334a89d6a66..1320d1ecc630 100644
--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -849,6 +849,7 @@ int cifs_readdir(struct file *file, struct dir_context *ctx)
 		 * if buggy server returns . and .. late do we want to
 		 * check for that here?
 		 */
+		*tmp_buf = 0;
 		rc = cifs_filldir(current_entry, file, ctx,
 				  tmp_buf, max_len);
 		if (rc) {