3.5.7.9 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: CQ Tang <[email protected]>

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 <[email protected]>
Link: 
http://lkml.kernel.org/r/[email protected]
Signed-off-by: Mike Marciniszyn <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>
Signed-off-by: Luis Henriques <[email protected]>
---
 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

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