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>
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index c6daaf6..c9267ac 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -627,10 +627,7 @@
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);