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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: 373cd784d0 ("metag: Memory handling")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: linux-metag@vger.kernel.org
Cc: stable@vger.kernel.org
This commit is contained in:
James Hogan 2017-03-31 11:23:18 +01:00
parent ef62a2d81f
commit 2257211942
1 changed files with 4 additions and 6 deletions
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10
arch/metag/lib/usercopy.c
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@ -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)) {