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Subject[tip:core/core] overflow.h: Add comment documenting __ab_c_size()
Commit-ID:  899cbdfa8d147c873fe4e66c38d2cca3c1ac6286
Gitweb: https://git.kernel.org/tip/899cbdfa8d147c873fe4e66c38d2cca3c1ac6286
Author: Rasmus Villemoes <linux@rasmusvillemoes.dk>
AuthorDate: Wed, 10 Apr 2019 22:27:25 +0200
Committer: Borislav Petkov <bp@suse.de>
CommitDate: Wed, 10 Apr 2019 22:35:47 +0200

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 <bp@suse.de>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Matthew Wilcox <willy@infradead.org>
Link: https://lkml.kernel.org/r/20190405045711.30339-1-bp@alien8.de
---
include/linux/overflow.h | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

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;
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