From: Andrey Ryabinin aryabinin@virtuozzo.com
commit 7f1e541fc8d57a143dd5df1d0a1276046e08c083 upstream.
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 aryabinin@virtuozzo.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [bwh: Backported to 4.4: adjust context] Signed-off-by: Ben Hutchings ben.hutchings@codethink.co.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/compiler.h | 8 ++++++++ 1 file changed, 8 insertions(+)
--- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -292,6 +292,7 @@ static __always_inline void __write_once * with an explicit memory barrier or atomic instruction that provides the * required ordering. */ +#include <linux/kasan-checks.h>
#define __READ_ONCE(x, check) \ ({ \ @@ -310,6 +311,13 @@ static __always_inline void __write_once */ #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 = \