From: Vasily Gorbik <gor@linux.ibm.com>
Date: Wed, 17 Jun 2020 15:05:49 +0200
Subject: s390/kasan: fix early pgm check handler execution
Git-commit: 998f5bbe3dbdab81c1cfb1aef7c3892f5d24f6c7
Patch-mainline: v5.8-rc3
References: git-fixes bsc#1211360

Currently if early_pgm_check_handler is called it ends up in pgm check
loop. The problem is that early_pgm_check_handler is instrumented by
KASAN but executed without DAT flag enabled which leads to addressing
exception when KASAN checks try to access shadow memory.

Fix that by executing early handlers with DAT flag on under KASAN as
expected.

Reported-and-tested-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Miroslav Franc <mfranc@suse.cz>
---
 arch/s390/kernel/early.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
index cd241ee66eff..078277231858 100644
--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -170,6 +170,8 @@ static noinline __init void setup_lowcore_early(void)
 	psw_t psw;
 
 	psw.mask = PSW_MASK_BASE | PSW_DEFAULT_KEY | PSW_MASK_EA | PSW_MASK_BA;
+	if (IS_ENABLED(CONFIG_KASAN))
+		psw.mask |= PSW_MASK_DAT;
 	psw.addr = (unsigned long) s390_base_ext_handler;
 	S390_lowcore.external_new_psw = psw;
 	psw.addr = (unsigned long) s390_base_pgm_handler;