linux-kernel - [PATCH 5.15 109/121] s390/boot: fix absolute zero lowcore corruption on boot

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Message-Id: <20220913140402.029966827@linuxfoundation.org>
Date:   Tue, 13 Sep 2022 16:05:00 +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 <hca@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 109/121] s390/boot: fix absolute zero lowcore corruption on boot

From: Alexander Gordeev <agordeev@...ux.ibm.com>

[ Upstream commit 12dd19c159659ec9050f45dc8a2ff3c3917f4be3 ]

Crash dump always starts on CPU0. In case CPU0 is offline the
prefix page is not installed and the absolute zero lowcore is
used. However, struct lowcore::mcesad is never assigned and
stays zero. That leads to __machine_kdump() -> save_vx_regs()
call silently stores vector registers to the absolute lowcore
at 0x11b0 offset.

Fixes: a62bc0739253 ("s390/kdump: add support for vector extension")
Reviewed-by: Heiko Carstens <hca@...ux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@...ux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/s390/kernel/nmi.c   | 2 +-
 arch/s390/kernel/setup.c | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/s390/kernel/nmi.c b/arch/s390/kernel/nmi.c
index a50f2ff1b00e8..383b4799b6dd3 100644
--- a/arch/s390/kernel/nmi.c
+++ b/arch/s390/kernel/nmi.c
@@ -62,7 +62,7 @@ static inline unsigned long nmi_get_mcesa_size(void)
  * The structure is required for machine check happening early in
  * the boot process.
  */
-static struct mcesa boot_mcesa __initdata __aligned(MCESA_MAX_SIZE);
+static struct mcesa boot_mcesa __aligned(MCESA_MAX_SIZE);
 
 void __init nmi_alloc_boot_cpu(struct lowcore *lc)
 {
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index 6b1a8697fae8d..4dfe37b068898 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -484,6 +484,7 @@ static void __init setup_lowcore_dat_off(void)
 	put_abs_lowcore(restart_data, lc->restart_data);
 	put_abs_lowcore(restart_source, lc->restart_source);
 	put_abs_lowcore(restart_psw, lc->restart_psw);
+	put_abs_lowcore(mcesad, lc->mcesad);
 
 	lc->spinlock_lockval = arch_spin_lockval(0);
 	lc->spinlock_index = 0;
-- 
2.35.1