Re: [PATCH] overflow: Make sure size helpers are always inlined

Re: [PATCH] overflow: Make sure size helpers are always inlined

[Gustavo A. R. Silva]

On 2/25/26 08:24, Kees Cook wrote:
> With kmalloc_obj() performing implicit size calculations, the embedded
> size_mul() calls, while marked inline, were not always being inlined.
> I noticed a couple places where allocations were making a call out for
> things that would otherwise be compile-time calculated. Force the
> compilers to always inline these calculations.
> 
> Signed-off-by: Kees Cook <kees@kernel.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks!
-Gustavo

> ---
> Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
> Cc: <linux-hardening@vger.kernel.org>
> ---
>   include/linux/overflow.h | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/overflow.h b/include/linux/overflow.h
> index eddd987a8513..a8cb6319b4fb 100644
> --- a/include/linux/overflow.h
> +++ b/include/linux/overflow.h
> @@ -42,7 +42,7 @@
>    * both the type-agnostic benefits of the macros while also being able to
>    * enforce that the return value is, in fact, checked.
>    */
> -static inline bool __must_check __must_check_overflow(bool overflow)
> +static __always_inline bool __must_check __must_check_overflow(bool overflow)
>   {
>   	return unlikely(overflow);
>   }
> @@ -327,7 +327,7 @@ static inline bool __must_check __must_check_overflow(bool overflow)
>    * with any overflow causing the return value to be SIZE_MAX. The
>    * lvalue must be size_t to avoid implicit type conversion.
>    */
> -static inline size_t __must_check size_mul(size_t factor1, size_t factor2)
> +static __always_inline size_t __must_check size_mul(size_t factor1, size_t factor2)
>   {
>   	size_t bytes;
>   
> @@ -346,7 +346,7 @@ static inline size_t __must_check size_mul(size_t factor1, size_t factor2)
>    * with any overflow causing the return value to be SIZE_MAX. The
>    * lvalue must be size_t to avoid implicit type conversion.
>    */
> -static inline size_t __must_check size_add(size_t addend1, size_t addend2)
> +static __always_inline size_t __must_check size_add(size_t addend1, size_t addend2)
>   {
>   	size_t bytes;
>   
> @@ -367,7 +367,7 @@ static inline size_t __must_check size_add(size_t addend1, size_t addend2)
>    * argument may be SIZE_MAX (or the result with be forced to SIZE_MAX).
>    * The lvalue must be size_t to avoid implicit type conversion.
>    */
> -static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
> +static __always_inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
>   {
>   	size_t bytes;
>   

[PATCH] overflow: Make sure size helpers are always inlined

[Kees Cook]

With kmalloc_obj() performing implicit size calculations, the embedded
size_mul() calls, while marked inline, were not always being inlined.
I noticed a couple places where allocations were making a call out for
things that would otherwise be compile-time calculated. Force the
compilers to always inline these calculations.

Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: <linux-hardening@vger.kernel.org>
---
 include/linux/overflow.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/overflow.h b/include/linux/overflow.h
index eddd987a8513..a8cb6319b4fb 100644
--- a/include/linux/overflow.h
+++ b/include/linux/overflow.h
@@ -42,7 +42,7 @@
  * both the type-agnostic benefits of the macros while also being able to
  * enforce that the return value is, in fact, checked.
  */
-static inline bool __must_check __must_check_overflow(bool overflow)
+static __always_inline bool __must_check __must_check_overflow(bool overflow)
 {
 	return unlikely(overflow);
 }
@@ -327,7 +327,7 @@ static inline bool __must_check __must_check_overflow(bool overflow)
  * with any overflow causing the return value to be SIZE_MAX. The
  * lvalue must be size_t to avoid implicit type conversion.
  */
-static inline size_t __must_check size_mul(size_t factor1, size_t factor2)
+static __always_inline size_t __must_check size_mul(size_t factor1, size_t factor2)
 {
 	size_t bytes;
 
@@ -346,7 +346,7 @@ static inline size_t __must_check size_mul(size_t factor1, size_t factor2)
  * with any overflow causing the return value to be SIZE_MAX. The
  * lvalue must be size_t to avoid implicit type conversion.
  */
-static inline size_t __must_check size_add(size_t addend1, size_t addend2)
+static __always_inline size_t __must_check size_add(size_t addend1, size_t addend2)
 {
 	size_t bytes;
 
@@ -367,7 +367,7 @@ static inline size_t __must_check size_add(size_t addend1, size_t addend2)
  * argument may be SIZE_MAX (or the result with be forced to SIZE_MAX).
  * The lvalue must be size_t to avoid implicit type conversion.
  */
-static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
+static __always_inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
 {
 	size_t bytes;
 
-- 
2.34.1