[ 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 <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Sasha Levin <[email protected]> --- include/linux/compiler.h | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index ced454c03819..3050de0dac96 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -302,6 +302,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s * with an explicit memory barrier or atomic instruction that provides the * required ordering. */ +#include <linux/kasan-checks.h> #define __READ_ONCE(x, check) \ ({ \ @@ -320,6 +321,13 @@ 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 = \ -- 2.20.1
