linux-kernel - [PATCH 5.4 025/109] s390/kasan: fix early pgm check handler execution

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Message-Id: <20200714184106.735185073@linuxfoundation.org>
Date:   Tue, 14 Jul 2020 20:43:28 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Sasha Levin <sashal@...nel.org>,
        Alexander Egorenkov <egorenar@...ux.ibm.com>
Subject: [PATCH 5.4 025/109] s390/kasan: fix early pgm check handler execution

From: Vasily Gorbik <gor@...ux.ibm.com>

[ Upstream commit 998f5bbe3dbdab81c1cfb1aef7c3892f5d24f6c7 ]

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@...ux.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@...ibm.com>
Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 b432d63d0b373..2531776cf6cf9 100644
--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -169,6 +169,8 @@ 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;
-- 
2.25.1