Patch "metag/usercopy: Fix alignment error checking" has been added to the 4.4-stable tree

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

metag/usercopy: Fix alignment error checking

to the 4.4-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:
metag-usercopy-fix-alignment-error-checking.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: James Hogan <[email protected]>
Date: Fri, 31 Mar 2017 11:23:18 +0100
Subject: metag/usercopy: Fix alignment error checking

From: James Hogan <[email protected]>

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.

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

@@ -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)) {

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/mips-end-spinlocks-with-.insn.patch queue-4.4/metag-usercopy-add-missing-fixups.patch queue-4.4/metag-usercopy-add-early-abort-to-copy_to_user.patch queue-4.4/mips-ralink-fix-typos-in-rt3883-pinctrl.patch queue-4.4/metag-usercopy-set-flags-before-addz.patch queue-4.4/metag-usercopy-fix-src-fixup-in-from-user-rapf-loops.patch queue-4.4/metag-usercopy-drop-unused-macros.patch queue-4.4/mips-lantiq-fix-missing-xbar-kernel-panic.patch queue-4.4/metag-usercopy-zero-rest-of-buffer-from-copy_from_user.patch queue-4.4/metag-usercopy-fix-alignment-error-checking.patch queue-4.4/mips-force-o32-fp64-support-on-32bit-mips64r6-kernels.patch