[PATCH 5.4 125/191] s390: disable preemption when switching to nodat stack with CALL_ON_STACK

Greg Kroah-Hartman
2020-01-02T22:15:56Z

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

[ Upstream commit 7f28dad395243c5026d649136823bbc40029a828 ]

Make sure preemption is disabled when temporary switching to nodat
stack with CALL_ON_STACK helper, because nodat stack is per cpu.

Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/s390/kernel/machine_kexec.c | 2 ++
arch/s390/mm/maccess.c | 12 +++++++++---
2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/s390/kernel/machine_kexec.c b/arch/s390/kernel/machine_kexec.c
index d402ced7f7c3..cb8b1cc285c9 100644
--- a/arch/s390/kernel/machine_kexec.c
+++ b/arch/s390/kernel/machine_kexec.c
@@ -164,7 +164,9 @@ static bool kdump_csum_valid(struct kimage *image)
#ifdef CONFIG_CRASH_DUMP
int rc;

+ preempt_disable();
rc = CALL_ON_STACK(do_start_kdump, S390_lowcore.nodat_stack, 1, image);
+ preempt_enable();
return rc == 0;
#else
return false;
diff --git a/arch/s390/mm/maccess.c b/arch/s390/mm/maccess.c
index 59ad7997fed1..de7ca4b6718f 100644
--- a/arch/s390/mm/maccess.c
+++ b/arch/s390/mm/maccess.c
@@ -119,9 +119,15 @@ static unsigned long __no_sanitize_address _memcpy_real(unsigned long dest,
*/
int memcpy_real(void *dest, void *src, size_t count)
{
- if (S390_lowcore.nodat_stack != 0)
- return CALL_ON_STACK(_memcpy_real, S390_lowcore.nodat_stack,
- 3, dest, src, count);
+ int rc;
+
+ if (S390_lowcore.nodat_stack != 0) {
+ preempt_disable();
+ rc = CALL_ON_STACK(_memcpy_real, S390_lowcore.nodat_stack, 3,
+ dest, src, count);
+ preempt_enable();
+ return rc;
+ }
/*
* This is a really early memcpy_real call, the stacks are
* not set up yet. Just call _memcpy_real on the early boot
--
2.20.1