Patch "strscpy: zero any trailing garbage bytes in the destination" has been added to the 3.18-stable tree

Patch "strscpy: zero any trailing garbage bytes in the destination" has been added to the 3.18-stable tree

[gregkh]

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

    strscpy: zero any trailing garbage bytes in the destination

to the 3.18-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:
     strscpy-zero-any-trailing-garbage-bytes-in-the-destination.patch
and it can be found in the queue-3.18 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 990486c8af044f89bddfbde1d1cf9fde449bedbf Mon Sep 17 00:00:00 2001
From: Chris Metcalf <cmetcalf@ezchip.com>
Date: Tue, 6 Oct 2015 12:37:41 -0400
Subject: strscpy: zero any trailing garbage bytes in the destination

From: Chris Metcalf <cmetcalf@ezchip.com>

commit 990486c8af044f89bddfbde1d1cf9fde449bedbf upstream.

It's possible that the destination can be shadowed in userspace
(as, for example, the perf buffers are now).  So we should take
care not to leak data that could be inspected by userspace.

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 lib/string.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/lib/string.c
+++ b/lib/string.c
@@ -211,12 +211,13 @@ ssize_t strscpy(char *dest, const char *
 		unsigned long c, data;
 
 		c = *(unsigned long *)(src+res);
-		*(unsigned long *)(dest+res) = c;
 		if (has_zero(c, &data, &constants)) {
 			data = prep_zero_mask(c, data, &constants);
 			data = create_zero_mask(data);
+			*(unsigned long *)(dest+res) = c & zero_bytemask(data);
 			return res + find_zero(data);
 		}
+		*(unsigned long *)(dest+res) = c;
 		res += sizeof(unsigned long);
 		count -= sizeof(unsigned long);
 		max -= sizeof(unsigned long);


Patches currently in stable-queue which might be from cmetcalf@ezchip.com are

queue-3.18/strscpy-zero-any-trailing-garbage-bytes-in-the-destination.patch
queue-3.18/string-provide-strscpy.patch