Commit b63dbef9 authored Mar 04, 2015 by Mark Rutland Committed by Will Deacon Mar 19, 2015

arm64: fixmap: check idx is definitely valid



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>

parent 19fc5775

arch/arm64/mm/mmu.c

+1 −4

Original line number	Diff line number	Diff line
		@@ -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);