[ 3.5.y.z extended stable ] Patch "x86-64: Fix the failure case in copy_user_handle_tail()" has been added to staging queue

[Luis Henriques]

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

    x86-64: Fix the failure case in copy_user_handle_tail()

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

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

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 671ddaf23a32fa73d062180e47a53b335e180904 Mon Sep 17 00:00:00 2001
From: CQ Tang <cq.tang at intel.com>
Date: Mon, 18 Mar 2013 11:02:21 -0400
Subject: [PATCH] x86-64: Fix the failure case in copy_user_handle_tail()

commit 66db3feb486c01349f767b98ebb10b0c3d2d021b upstream.

The increment of "to" in copy_user_handle_tail() will have incremented
before a failure has been noted.  This causes us to skip a byte in the
failure case.

Only do the increment when assured there is no failure.

Signed-off-by: CQ Tang <cq.tang at intel.com>
Link: http://lkml.kernel.org/r/20130318150221.8439.993.stgit@phlsvslse11.ph.intel.com
Signed-off-by: Mike Marciniszyn <mike.marciniszyn at intel.com>
Signed-off-by: H. Peter Anvin <hpa at linux.intel.com>
Luis Henriques <luis.henriques at canonical.com>
---
 arch/x86/lib/usercopy_64.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index e5b130b..cc9de31 100644
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -72,10 +72,10 @@ copy_user_handle_tail(char *to, char *from, unsigned len, unsigned zerorest)
 	char c;
 	unsigned zero_len;

-	for (; len; --len) {
+	for (; len; --len, to++) {
 		if (__get_user_nocheck(c, from++, sizeof(char)))
 			break;
-		if (__put_user_nocheck(c, to++, sizeof(char)))
+		if (__put_user_nocheck(c, to, sizeof(char)))
 			break;
 	}

--
1.8.1.2