From 92d23c6e94157739b997cacce151586a0d07bb8a Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Fri, 26 Aug 2022 09:21:16 -0700 Subject: overflow, tracing: Define the is_signed_type() macro once There are two definitions of the is_signed_type() macro: one in and a second definition in . As suggested by Linus Torvalds, move the definition of the is_signed_type() macro into the header file. Change the definition of the is_signed_type() macro to make sure that it does not trigger any sparse warnings with future versions of sparse for bitwise types. See also: https://lore.kernel.org/all/CAHk-=whjH6p+qzwUdx5SOVVHjS3WvzJQr6mDUwhEyTf6pJWzaQ@mail.gmail.com/ https://lore.kernel.org/all/CAHk-=wjQGnVfb4jehFR0XyZikdQvCZouE96xR_nnf5kqaM5qqQ@mail.gmail.com/ Cc: Andrew Morton Cc: Arnd Bergmann Cc: Dan Williams Cc: Eric Dumazet Cc: Ingo Molnar Cc: Isabella Basso Cc: "Jason A. Donenfeld" Cc: Josh Poimboeuf Cc: Luc Van Oostenryck Cc: Masami Hiramatsu Cc: Nathan Chancellor Cc: Peter Zijlstra Cc: Rasmus Villemoes Cc: Sander Vanheule Cc: Steven Rostedt Cc: Vlastimil Babka Cc: Yury Norov Signed-off-by: Bart Van Assche Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20220826162116.1050972-3-bvanassche@acm.org --- include/linux/overflow.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include/linux/overflow.h') diff --git a/include/linux/overflow.h b/include/linux/overflow.h index f1221d11f8e5..0eb3b192f07a 100644 --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -30,7 +30,6 @@ * https://mail-index.netbsd.org/tech-misc/2007/02/05/0000.html - * credit to Christian Biere. */ -#define is_signed_type(type) (((type)(-1)) < (type)1) #define __type_half_max(type) ((type)1 << (8*sizeof(type) - 1 - is_signed_type(type))) #define type_max(T) ((T)((__type_half_max(T) - 1) + __type_half_max(T))) #define type_min(T) ((T)((T)-type_max(T)-(T)1)) -- cgit From d219d2a9a92e39aa92799efe8f2aa21259b6dd82 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Mon, 29 Aug 2022 13:37:17 -0700 Subject: overflow: Allow mixed type arguments When the check_[op]_overflow() helpers were introduced, all arguments were required to be the same type to make the fallback macros simpler. However, now that the fallback macros have been removed[1], it is fine to allow mixed types, which makes using the helpers much more useful, as they can be used to test for type-based overflows (e.g. adding two large ints but storing into a u8), as would be handy in the drm core[2]. Remove the restriction, and add additional self-tests that exercise some of the mixed-type overflow cases, and double-check for accidental macro side-effects. [1] https://git.kernel.org/linus/4eb6bd55cfb22ffc20652732340c4962f3ac9a91 [2] https://lore.kernel.org/lkml/20220824084514.2261614-2-gwan-gyeong.mun@intel.com Cc: Rasmus Villemoes Cc: Gwan-gyeong Mun Cc: "Gustavo A. R. Silva" Cc: Nick Desaulniers Cc: linux-hardening@vger.kernel.org Reviewed-by: Andrzej Hajda Reviewed-by: Gwan-gyeong Mun Tested-by: Gwan-gyeong Mun Signed-off-by: Kees Cook --- include/linux/overflow.h | 72 +++++++++++++++++++++++++++--------------------- 1 file changed, 41 insertions(+), 31 deletions(-) (limited to 'include/linux/overflow.h') diff --git a/include/linux/overflow.h b/include/linux/overflow.h index 0eb3b192f07a..19dfdd74835e 100644 --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -51,40 +51,50 @@ static inline bool __must_check __must_check_overflow(bool overflow) return unlikely(overflow); } -/* - * For simplicity and code hygiene, the fallback code below insists on - * a, b and *d having the same type (similar to the min() and max() - * macros), whereas gcc's type-generic overflow checkers accept - * different types. Hence we don't just make check_add_overflow an - * alias for __builtin_add_overflow, but add type checks similar to - * below. +/** check_add_overflow() - Calculate addition with overflow checking + * + * @a: first addend + * @b: second addend + * @d: pointer to store sum + * + * Returns 0 on success. + * + * *@d holds the results of the attempted addition, but is not considered + * "safe for use" on a non-zero return value, which indicates that the + * sum has overflowed or been truncated. */ -#define check_add_overflow(a, b, d) __must_check_overflow(({ \ - typeof(a) __a = (a); \ - typeof(b) __b = (b); \ - typeof(d) __d = (d); \ - (void) (&__a == &__b); \ - (void) (&__a == __d); \ - __builtin_add_overflow(__a, __b, __d); \ -})) +#define check_add_overflow(a, b, d) \ + __must_check_overflow(__builtin_add_overflow(a, b, d)) -#define check_sub_overflow(a, b, d) __must_check_overflow(({ \ - typeof(a) __a = (a); \ - typeof(b) __b = (b); \ - typeof(d) __d = (d); \ - (void) (&__a == &__b); \ - (void) (&__a == __d); \ - __builtin_sub_overflow(__a, __b, __d); \ -})) +/** check_sub_overflow() - Calculate subtraction with overflow checking + * + * @a: minuend; value to subtract from + * @b: subtrahend; value to subtract from @a + * @d: pointer to store difference + * + * Returns 0 on success. + * + * *@d holds the results of the attempted subtraction, but is not considered + * "safe for use" on a non-zero return value, which indicates that the + * difference has underflowed or been truncated. + */ +#define check_sub_overflow(a, b, d) \ + __must_check_overflow(__builtin_sub_overflow(a, b, d)) -#define check_mul_overflow(a, b, d) __must_check_overflow(({ \ - typeof(a) __a = (a); \ - typeof(b) __b = (b); \ - typeof(d) __d = (d); \ - (void) (&__a == &__b); \ - (void) (&__a == __d); \ - __builtin_mul_overflow(__a, __b, __d); \ -})) +/** check_mul_overflow() - Calculate multiplication with overflow checking + * + * @a: first factor + * @b: second factor + * @d: pointer to store product + * + * Returns 0 on success. + * + * *@d holds the results of the attempted multiplication, but is not + * considered "safe for use" on a non-zero return value, which indicates + * that the product has overflowed or been truncated. + */ +#define check_mul_overflow(a, b, d) \ + __must_check_overflow(__builtin_mul_overflow(a, b, d)) /** check_shl_overflow() - Calculate a left-shifted value and check overflow * -- cgit