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Subject[PATCH 3.18 118/124] metag/usercopy: Fix alignment error checking
Date
3.18-stable review patch.  If anyone has any objections, please let me know.

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

From: James Hogan <james.hogan@imgtec.com>

commit 2257211942bbbf6c798ab70b487d7e62f7835a1a upstream.

Fix the error checking of the alignment adjustment code in
raw_copy_from_user(), which mistakenly considers it safe to skip the
error check when aligning the source buffer on a 2 or 4 byte boundary.

If the destination buffer was unaligned it may have started to copy
using byte or word accesses, which could well be at the start of a new
(valid) source page. This would result in it appearing to have copied 1
or 2 bytes at the end of the first (invalid) page rather than none at
all.

Fixes: 373cd784d0fc ("metag: Memory handling")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: linux-metag@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/metag/lib/usercopy.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)

--- a/arch/metag/lib/usercopy.c
+++ b/arch/metag/lib/usercopy.c
@@ -717,6 +717,8 @@ unsigned long __copy_user_zeroing(void *
if ((unsigned long) src & 1) {
__asm_copy_from_user_1(dst, src, retn);
n--;
+ if (retn)
+ goto copy_exception_bytes;
}
if ((unsigned long) dst & 1) {
/* Worst case - byte copy */
@@ -730,6 +732,8 @@ unsigned long __copy_user_zeroing(void *
if (((unsigned long) src & 2) && n >= 2) {
__asm_copy_from_user_2(dst, src, retn);
n -= 2;
+ if (retn)
+ goto copy_exception_bytes;
}
if ((unsigned long) dst & 2) {
/* Second worst case - word copy */
@@ -741,12 +745,6 @@ unsigned long __copy_user_zeroing(void *
}
}

- /* We only need one check after the unalignment-adjustments,
- because if both adjustments were done, either both or
- neither reference had an exception. */
- if (retn != 0)
- goto copy_exception_bytes;
-
#ifdef USE_RAPF
/* 64 bit copy loop */
if (!(((unsigned long) src | (unsigned long) dst) & 7)) {

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