On Mon, Jan 22, 2024 at 04:26:46PM -0800, Kees Cook wrote:
> Annotate atomic_add_return() and atomic_sub_return() to avoid signed
> overflow instrumentation. They are expected to wrap around.
>
> Cc: Will Deacon <w...@kernel.org>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Boqun Feng <boqun.f...@gmail.com>
> Cc: Mark Rutland <mark.rutl...@arm.com>
> Cc: Catalin Marinas <catalin.mari...@arm.com>
> Cc: linux-arm-ker...@lists.infradead.org
> Signed-off-by: Kees Cook <keesc...@chromium.org>
> ---
> arch/arm64/include/asm/atomic_lse.h | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/include/asm/atomic_lse.h
> b/arch/arm64/include/asm/atomic_lse.h
> index 87f568a94e55..30572458d702 100644
> --- a/arch/arm64/include/asm/atomic_lse.h
> +++ b/arch/arm64/include/asm/atomic_lse.h
> @@ -79,13 +79,13 @@ ATOMIC_FETCH_OP_SUB( )
> #undef ATOMIC_FETCH_OP_SUB
>
> #define ATOMIC_OP_ADD_SUB_RETURN(name)
> \
> -static __always_inline int \
> +static __always_inline __signed_wrap int \
> __lse_atomic_add_return##name(int i, atomic_t *v) \
> { \
> return __lse_atomic_fetch_add##name(i, v) + i; \
> } \
I'd strongly prefer using add_wrap() rather than annotating the function, i.e.
make this:
static __always_inline int \
__lse_atomic_add_return##name(int i, atomic_t *v) \
{ \
return add_wrap(__lse_atomic_fetch_add##name(i, v), i); \
} \
Likewise for the other instances below.
With that, this looks fine to me.
Mark.
> \
> -static __always_inline int \
> +static __always_inline __signed_wrap int \
> __lse_atomic_sub_return##name(int i, atomic_t *v) \
> { \
> return __lse_atomic_fetch_sub(i, v) - i; \
> @@ -186,13 +186,13 @@ ATOMIC64_FETCH_OP_SUB( )
> #undef ATOMIC64_FETCH_OP_SUB
>
> #define ATOMIC64_OP_ADD_SUB_RETURN(name) \
> -static __always_inline long \
> +static __always_inline __signed_wrap long \
> __lse_atomic64_add_return##name(s64 i, atomic64_t *v)
> \
> { \
> return __lse_atomic64_fetch_add##name(i, v) + i; \
> } \
> \
> -static __always_inline long \
> +static __always_inline __signed_wrap long \
> __lse_atomic64_sub_return##name(s64 i, atomic64_t *v)
> \
> { \
> return __lse_atomic64_fetch_sub##name(i, v) - i; \
> --
> 2.34.1
>
