| Message ID | 20240123002814.1396804-40-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | overflow: Refactor open-coded arithmetic wrap-around | expand |
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.marinas@arm.com> > Cc: Will Deacon <will@kernel.org> > Cc: Kalesh Singh <kaleshsingh@google.com> > Cc: Fuad Tabba <tabba@google.com> > Cc: Mark Brown <broonie@kernel.org> > Cc: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com> > Cc: Marc Zyngier <maz@kernel.org> > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: linux-arm-kernel@lists.infradead.org > Signed-off-by: Kees Cook <keescook@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.rutland@arm.com> Mark. > > return true; > -- > 2.34.1 >
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; return true;
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.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Fuad Tabba <tabba@google.com> Cc: Mark Brown <broonie@kernel.org> Cc: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Kees Cook <keescook@chromium.org> --- arch/arm64/include/asm/stacktrace/common.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)