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Commit 22572119 authored by James Hogan's avatar James Hogan
Browse files

metag/usercopy: Fix alignment error checking 



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: 373cd784 ("metag: Memory handling")
Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
Cc: linux-metag@vger.kernel.org
Cc: stable@vger.kernel.org
parent ef62a2d8

arch/metag/lib/usercopy.c

+4 −6
Original line number Diff line number Diff line
@@ -717,6 +717,8 @@ unsigned long __copy_user_zeroing(void *pdst, const void __user *psrc, 
	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 *pdst, const void __user *psrc, 
	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 *pdst, const void __user *psrc, 
		}

	}



	/* 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)) {