On Mon, Jan 22, 2024 at 04:27:15PM -0800, Kees Cook wrote: > In an effort to separate intentional arithmetic wrap-around from > unexpected wrap-around, we need to refactor places that depend on this > kind of math. One of the most common code patterns of this is: > > VAR + value < VAR > > Notably, this is considered "undefined behavior" for signed and pointer > types, which the kernel works around by using the -fno-strict-overflow > option in the build[1] (which used to just be -fwrapv). Regardless, we > want to get the kernel source to the position where we can meaningfully > instrument arithmetic wrap-around conditions and catch them when they > are unexpected, regardless of whether they are signed[2], unsigned[3], > or pointer[4] types. > > Refactor open-coded wrap-around addition test to use add_would_overflow(). > This paves the way to enabling the wrap-around sanitizers in the future. > > Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 > [1] > Link: https://github.com/KSPP/linux/issues/26 [2] > Link: https://github.com/KSPP/linux/issues/27 [3] > Link: https://github.com/KSPP/linux/issues/344 [4] > Cc: Catalin Marinas <catalin.mari...@arm.com> > Cc: Will Deacon <w...@kernel.org> > Cc: Kalesh Singh <kaleshsi...@google.com> > Cc: Fuad Tabba <ta...@google.com> > Cc: Mark Brown <broo...@kernel.org> > Cc: "Madhavan T. Venkataraman" <madve...@linux.microsoft.com> > Cc: Marc Zyngier <m...@kernel.org> > Cc: Mark Rutland <mark.rutl...@arm.com> > Cc: linux-arm-ker...@lists.infradead.org > Signed-off-by: Kees Cook <keesc...@chromium.org> > --- > arch/arm64/include/asm/stacktrace/common.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/stacktrace/common.h > b/arch/arm64/include/asm/stacktrace/common.h > index f63dc654e545..6e0cb84961f8 100644 > --- a/arch/arm64/include/asm/stacktrace/common.h > +++ b/arch/arm64/include/asm/stacktrace/common.h > @@ -49,7 +49,7 @@ static inline bool stackinfo_on_stack(const struct > stack_info *info, > if (!info->low) > return false; > > - if (sp < info->low || sp + size < sp || sp + size > info->high) > + if (sp < info->low || add_would_overflow(sp, size) || sp + size > > info->high) > return false;
This looks fine to me, so FWIW: Acked-by: Mark Rutland <mark.rutl...@arm.com> Mark. > > return true; > -- > 2.34.1 >
