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arm64: fixmap: check idx is definitely valid

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Fixmap indices are in the interval (FIX_HOLE, __end_of_fixed_addresses),
but in __set_fixmap we only check idx <= __end_of_fixed_addresses, and
therefore indices <= FIX_HOLE are erroneously accepted. If called with
such an idx, __set_fixmap may corrupt page tables outside of the fixmap
region.

This patch ensures that we validate the idx against both endpoints of
the interval.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Kees Cook <keescook@chromium.org>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Laura Abbott <lauraa@codeaurora.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Mark Rutland 2015-03-04 13:27:35 +00:00 committed by Will Deacon
parent 19fc577579
commit b63dbef93f
1 changed files with 1 additions and 4 deletions
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5
arch/arm64/mm/mmu.c
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@ -627,10 +627,7 @@ void __set_fixmap(enum fixed_addresses idx,
unsigned long addr = __fix_to_virt(idx);
pte_t *pte;
if (idx >= __end_of_fixed_addresses) {
BUG();
return;
}
BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);
pte = fixmap_pte(addr);