evm: mark evm_fixmode as __ro_after_init

stable inclusion
from stable-5.10.80
commit c7400e2ec8de2cf0f8a858aeeaec2722106b2aab
bugzilla: 185821 https://gitee.com/openeuler/kernel/issues/I4L7CG

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c7400e2ec8de2cf0f8a858aeeaec2722106b2aab

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

commit 32ba540f upstream.

The evm_fixmode is only configurable by command-line option and it is never
modified outside initcalls, so declaring it with __ro_after_init is better.
Signed-off-by: NAustin Kim <austin.kim@lge.com>
Cc: stable@vger.kernel.org
Signed-off-by: NMimi Zohar <zohar@linux.ibm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Reviewed-by: NWeilong Chen <chenweilong@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

security/integrity/evm/evm_main.c

@@ -56,7 +56,7 @@ static struct xattr_list evm_config_default_xattrnames[] = {
 
 LIST_HEAD(evm_config_xattrnames);
 
-static int evm_fixmode;
+static int evm_fixmode __ro_after_init;
 static int __init evm_set_param(char *str)
 {
 	if (strncmp(str, "fix", 3) == 0)