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| author | Kees Cook <keescook@chromium.org> | 2024-01-26 22:09:50 -0800 |
|---|---|---|
| committer | Kees Cook <keescook@chromium.org> | 2024-02-29 13:38:01 -0800 |
| commit | 08d45ee84bb2650e237e150caca87cc4ded9b3e2 (patch) | |
| tree | 0f0474672597c717e276bcd41242f7d50535aa9c /include/linux/overflow.h | |
| parent | d70de8054c58d7bd9a4654c9f4797d29fa46d545 (diff) | |
| download | lwn-08d45ee84bb2650e237e150caca87cc4ded9b3e2.tar.gz lwn-08d45ee84bb2650e237e150caca87cc4ded9b3e2.zip | |
overflow: Introduce wrapping_assign_add() and wrapping_assign_sub()
This allows replacements of the idioms "var += offset" and "var -=
offset" with the wrapping_assign_add() and wrapping_assign_sub() helpers
respectively. They will avoid wrap-around sanitizer instrumentation.
Add to the selftests to validate behavior and lack of side-effects.
Reviewed-by: Marco Elver <elver@google.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'include/linux/overflow.h')
| -rw-r--r-- | include/linux/overflow.h | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/include/linux/overflow.h b/include/linux/overflow.h index d3ff8e2bec29..dede374832c9 100644 --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -82,6 +82,22 @@ static inline bool __must_check __must_check_overflow(bool overflow) }) /** + * wrapping_assign_add() - Intentionally perform a wrapping increment assignment + * @var: variable to be incremented + * @offset: amount to add + * + * Increments @var by @offset with wrap-around. Returns the resulting + * value of @var. Will not trip any wrap-around sanitizers. + * + * Returns the new value of @var. + */ +#define wrapping_assign_add(var, offset) \ + ({ \ + typeof(var) *__ptr = &(var); \ + *__ptr = wrapping_add(typeof(var), *__ptr, offset); \ + }) + +/** * check_sub_overflow() - Calculate subtraction with overflow checking * @a: minuend; value to subtract from * @b: subtrahend; value to subtract from @a @@ -112,6 +128,22 @@ static inline bool __must_check __must_check_overflow(bool overflow) }) /** + * wrapping_assign_sub() - Intentionally perform a wrapping decrement assign + * @var: variable to be decremented + * @offset: amount to subtract + * + * Decrements @var by @offset with wrap-around. Returns the resulting + * value of @var. Will not trip any wrap-around sanitizers. + * + * Returns the new value of @var. + */ +#define wrapping_assign_sub(var, offset) \ + ({ \ + typeof(var) *__ptr = &(var); \ + *__ptr = wrapping_sub(typeof(var), *__ptr, offset); \ + }) + +/** * check_mul_overflow() - Calculate multiplication with overflow checking * @a: first factor * @b: second factor |