From 25ea5fd2ee9defdd3964a172ea25164ca4056955 Mon Sep 17 00:00:00 2001 From: Andrey Ryabinin Date: Thu, 1 Feb 2018 21:00:49 +0300 Subject: [PATCH] compiler.h: Add read_word_at_a_time() function. BugLink: https://bugs.launchpad.net/bugs/1839036 [ Upstream commit 7f1e541fc8d57a143dd5df1d0a1276046e08c083 ] Sometimes we know that it's safe to do potentially out-of-bounds access because we know it won't cross a page boundary. Still, KASAN will report this as a bug. Add read_word_at_a_time() function which is supposed to be used in such cases. In read_word_at_a_time() KASAN performs relaxed check - only the first byte of access is validated. Signed-off-by: Andrey Ryabinin Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin Signed-off-by: Kamal Mostafa Signed-off-by: Khalid Elmously --- include/linux/compiler.h | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 4d41730ec974..c062238f408c 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -243,6 +243,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s * required ordering. */ #include +#include #define __READ_ONCE(x, check) \ ({ \ @@ -262,6 +263,13 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s */ #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0) +static __no_kasan_or_inline +unsigned long read_word_at_a_time(const void *addr) +{ + kasan_check_read(addr, 1); + return *(unsigned long *)addr; +} + #define WRITE_ONCE(x, val) \ ({ \ union { typeof(x) __val; char __c[1]; } __u = \ -- 2.39.2