From dc7fe518b0493faa0af0568d6d8c2a33c00f58d0 Mon Sep 17 00:00:00 2001 From: Leon Romanovsky Date: Sun, 17 Mar 2019 12:11:14 +0200 Subject: overflow: Fix -Wtype-limits compilation warnings Attempt to use check_shl_overflow() with inputs of unsigned type produces the following compilation warnings. drivers/infiniband/hw/mlx5/qp.c: In function _set_user_rq_size_: ./include/linux/overflow.h:230:6: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits] _s >= 0 && _s < 8 * sizeof(*d) ? _s : 0; \ ^~ drivers/infiniband/hw/mlx5/qp.c:5820:6: note: in expansion of macro _check_shl_overflow_ if (check_shl_overflow(rwq->wqe_count, rwq->wqe_shift, &rwq->buf_size)) ^~~~~~~~~~~~~~~~~~ ./include/linux/overflow.h:232:26: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits] (_to_shift != _s || *_d < 0 || _a < 0 || \ ^ drivers/infiniband/hw/mlx5/qp.c:5820:6: note: in expansion of macro _check_shl_overflow_ if (check_shl_overflow(rwq->wqe_count, rwq->wqe_shift, &rwq->buf_size)) ^~~~~~~~~~~~~~~~~~ ./include/linux/overflow.h:232:36: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits] (_to_shift != _s || *_d < 0 || _a < 0 || \ ^ drivers/infiniband/hw/mlx5/qp.c:5820:6: note: in expansion of macro _check_shl_overflow_ if (check_shl_overflow(rwq->wqe_count, rwq->wqe_shift,&rwq->buf_size)) ^~~~~~~~~~~~~~~~~~ Fixes: 0c66847793d1 ("overflow.h: Add arithmetic shift helper") Reviewed-by: Bart Van Assche Acked-by: Kees Cook Signed-off-by: Leon Romanovsky Signed-off-by: Jason Gunthorpe --- include/linux/overflow.h | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) (limited to 'include/linux/overflow.h') diff --git a/include/linux/overflow.h b/include/linux/overflow.h index 40b48e2133cb..15eb85de9226 100644 --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -36,6 +36,12 @@ #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)) +/* + * Avoids triggering -Wtype-limits compilation warning, + * while using unsigned data types to check a < 0. + */ +#define is_non_negative(a) ((a) > 0 || (a) == 0) +#define is_negative(a) (!(is_non_negative(a))) #ifdef COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW /* @@ -227,10 +233,10 @@ typeof(d) _d = d; \ u64 _a_full = _a; \ unsigned int _to_shift = \ - _s >= 0 && _s < 8 * sizeof(*d) ? _s : 0; \ + is_non_negative(_s) && _s < 8 * sizeof(*d) ? _s : 0; \ *_d = (_a_full << _to_shift); \ - (_to_shift != _s || *_d < 0 || _a < 0 || \ - (*_d >> _to_shift) != _a); \ + (_to_shift != _s || is_negative(*_d) || is_negative(_a) || \ + (*_d >> _to_shift) != _a); \ }) /** -- cgit From e0478542cfd4d993e38d5f92a3f3ecd238805e96 Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Wed, 10 Apr 2019 22:27:25 +0200 Subject: overflow.h: Add comment documenting __ab_c_size() __ab_c_size() is a somewhat opaque name. Document its purpose, and while at it, rename the parameters to actually match the abc naming. [ bp: glued a complete patch from chunks on LKML. ] Reported-by: Borislav Petkov Signed-off-by: Rasmus Villemoes Signed-off-by: Borislav Petkov Acked-by: Kees Cook Cc: Matthew Wilcox Link: https://lkml.kernel.org/r/20190405045711.30339-1-bp@alien8.de --- include/linux/overflow.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'include/linux/overflow.h') diff --git a/include/linux/overflow.h b/include/linux/overflow.h index 40b48e2133cb..6534a727cadb 100644 --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -278,11 +278,15 @@ static inline __must_check size_t array3_size(size_t a, size_t b, size_t c) return bytes; } -static inline __must_check size_t __ab_c_size(size_t n, size_t size, size_t c) +/* + * Compute a*b+c, returning SIZE_MAX on overflow. Internal helper for + * struct_size() below. + */ +static inline __must_check size_t __ab_c_size(size_t a, size_t b, size_t c) { size_t bytes; - if (check_mul_overflow(n, size, &bytes)) + if (check_mul_overflow(a, b, &bytes)) return SIZE_MAX; if (check_add_overflow(bytes, c, &bytes)) return SIZE_MAX; -- cgit