livepatch/x86: Fix incorrect use of 'strncpy'

hulk inclusion
category: bugfix
bugzilla: 186253, https://gitee.com/openeuler/kernel/issues/I4TYA9


CVE: NA

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

Refer to following codes, 'strncpy' would stop copying if Null character
encountered. For example, when 'code' is "53 be 00 0a 05", 'old_code'
would be "53 be 00 00 00".
    > 276 static unsigned char *klp_old_code(unsigned char *code)
    > 277 {
    > 278         static union klp_code_union old_code;
    > 279
    > 280         strncpy(old_code.code, code, JMP_E9_INSN_SIZE);
    > 281         return old_code.code;
    > 282 }

As a result, the instructions cannot be restored completely, and the
system becomes abnormal.

Fixes: 7e2ab91e ("livepatch/x86: support livepatch without ftrace")
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Reviewed-by: Kuohai Xu <xukuohai@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>

arch/x86/kernel/livepatch.c

@@ -277,7 +277,7 @@ static unsigned char *klp_old_code(unsigned char *code)
 {
 	static union klp_code_union old_code;
 
-	strncpy(old_code.code, code, JMP_E9_INSN_SIZE);
+	memcpy(old_code.code, code, JMP_E9_INSN_SIZE);
 	return old_code.code;
 }