[PATCH AUTOSEL 4.9 2/4] audit: fix undefined behavior in bit shift for AUDIT_BIT

[Sasha Levin]

From: Gaosheng Cui <cuigaosheng1 at huawei.com>

[ Upstream commit 986d93f55bdeab1cac858d1e47b41fac10b2d7f6 ]

Shifting signed 32-bit value by 31 bits is undefined, so changing
significant bit to unsigned. The UBSAN warning calltrace like below:

UBSAN: shift-out-of-bounds in kernel/auditfilter.c:179:23
left shift of 1 by 31 places cannot be represented in type 'int'
Call Trace:
 <TASK>
 dump_stack_lvl+0x7d/0xa5
 dump_stack+0x15/0x1b
 ubsan_epilogue+0xe/0x4e
 __ubsan_handle_shift_out_of_bounds+0x1e7/0x20c
 audit_register_class+0x9d/0x137
 audit_classes_init+0x4d/0xb8
 do_one_initcall+0x76/0x430
 kernel_init_freeable+0x3b3/0x422
 kernel_init+0x24/0x1e0
 ret_from_fork+0x1f/0x30
 </TASK>

Signed-off-by: Gaosheng Cui <cuigaosheng1 at huawei.com>
[PM: remove bad 'Fixes' tag as issue predates git, added in v2.6.6-rc1]
Signed-off-by: Paul Moore <paul at paul-moore.com>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 include/uapi/linux/audit.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index 208df7b44e90..d7ac6b9be18e 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -170,7 +170,7 @@
 #define AUDIT_MAX_KEY_LEN  256
 #define AUDIT_BITMASK_SIZE 64
 #define AUDIT_WORD(nr) ((__u32)((nr)/32))
-#define AUDIT_BIT(nr)  (1 << ((nr) - AUDIT_WORD(nr)*32))
+#define AUDIT_BIT(nr)  (1U << ((nr) - AUDIT_WORD(nr)*32))
 
 #define AUDIT_SYSCALL_CLASSES 16
 #define AUDIT_CLASS_DIR_WRITE 0
-- 
2.35.1