x86/uaccess: Move variable into switch case statement

stable inclusion
from stable-v5.10.94
commit d21b47c607379c50924f961ea45cdb7702bf8007
bugzilla: https://gitee.com/openeuler/kernel/issues/I531X9

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d21b47c607379c50924f961ea45cdb7702bf8007

--------------------------------

[ Upstream commit 61646ca8 ]

When building with automatic stack variable initialization, GCC 12
complains about variables defined outside of switch case statements.
Move the variable into the case that uses it, which silences the warning:

./arch/x86/include/asm/uaccess.h:317:23: warning: statement will never be executed [-Wswitch-unreachable]
  317 |         unsigned char x_u8__; \
      |                       ^~~~~~

Fixes: 865c50e1 ("x86/uaccess: utilize CONFIG_CC_HAS_ASM_GOTO_OUTPUT")
Signed-off-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NDave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211209043456.1377875-1-keescook@chromium.orgSigned-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

arch/x86/include/asm/uaccess.h

@@ -314,11 +314,12 @@ do {									\
 do {									\
 	__chk_user_ptr(ptr);						\
 	switch (size) {							\
-	unsigned char x_u8__;						\
-	case 1:								\
+	case 1:	{							\
+		unsigned char x_u8__;					\
 		__get_user_asm(x_u8__, ptr, "b", "=q", label);		\
 		(x) = x_u8__;						\
 		break;							\
+	}								\
 	case 2:								\
 		__get_user_asm(x, ptr, "w", "=r", label);		\
 		break;							\