arm64: Mark __stack_chk_guard as __ro_after_init

stable inclusion
from linux-4.19.209
commit 93cb263d81bc9b67abd2e250a3caa21fb983a5e1

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

[ Upstream commit 9fcb2e93 ]

__stack_chk_guard is setup once while init stage and never changed
after that.

Although the modification of this variable at runtime will usually
cause the kernel to crash (so does the attacker), it should be marked
as __ro_after_init, and it should not affect performance if it is
placed in the ro_after_init section.
Signed-off-by: NDan Li <ashimida@linux.alibaba.com>
Acked-by: NMark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/1631612642-102881-1-git-send-email-ashimida@linux.alibaba.comSigned-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Acked-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

arch/arm64/kernel/process.c

@@ -62,7 +62,7 @@
 
 #ifdef CONFIG_STACKPROTECTOR
 #include <linux/stackprotector.h>
-unsigned long __stack_chk_guard __read_mostly;
+unsigned long __stack_chk_guard __ro_after_init;
 EXPORT_SYMBOL(__stack_chk_guard);
 #endif