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FAILED: patch "[PATCH] KVM: s390: Fix memory corruption by not reinjecting CK" failed to apply to 6.1-stable tree

PATCH New [email protected] 2 participants 3 messages Sep 9 – Sep 11

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Stable branch s390 KVM s390
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#0 lore raw

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 546dde823a36d7283dcf46127c2f3d093443860f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090945-quirk-camping-07b3@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 546dde823a36d7283dcf46127c2f3d093443860f Mon Sep 17 00:00:00 2001
From: Christian Borntraeger <[email protected]>
Date: Thu, 6 Aug 2026 16:58:35 +0200
Subject: [PATCH] KVM: s390: Fix memory corruption by not reinjecting CK
machine checks

Channel-subsystem damage machine checks are for the host channel subsystem. The guest channel subsystem is emulated in the userspace VMM. There is no point in forwarding such machine checks into the guest.

This also simplifies the machine check reinjection and avoids kfree of a stack variable as reported by sashiko. There might be still machine checks that have the ck bit set with another bit (like instruction damage), mask out the CK bit in s390_backup_mcck_info(), like the CP and ED bits already are.

Fixes 4d62fcc0b692 ("KVM: s390: Inject machine check into the guest")
Cc [email protected]
Signed-off-by Christian Borntraeger <[email protected]>
Acked-by Heiko Carstens <[email protected]>
Acked-by Claudio Imbrenda <[email protected]>
Signed-off-by Claudio Imbrenda <[email protected]>

Message-ID: <[email protected]>

arch/s390/include/asm/nmi.h +3 -0
index 6454c1531854..7919b2b9ac9c 100644
@@ -22,6 +22,7 @@
 #define MCCK_CODE_SYSTEM_DAMAGE		BIT(63)
 #define MCCK_CODE_EXT_DAMAGE		BIT(63 - 5)
 #define MCCK_CODE_CP			BIT(63 - 9)
+#define MCCK_CODE_CK			BIT(63 - 11)
 #define MCCK_CODE_STG_ERROR		BIT(63 - 16)
 #define MCCK_CODE_STG_KEY_ERROR		BIT(63 - 18)
 #define MCCK_CODE_STG_DEGRAD		BIT(63 - 19)

@@ -33,6 +34,8 @@
 #define MCCK_CODE_FC_VALID		BIT(63 - 43)
 #define MCCK_CODE_CPU_TIMER_VALID	BIT(63 - 46)
 
+#define MCCK_CODE_NO_GUEST	(MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE | MCCK_CODE_CK)
+
 #ifndef __ASSEMBLER__
 
 union mci {
arch/s390/kernel/nmi.c +1 -4
index e17a59d4d5a4..17297a8b63d9 100644
@@ -344,8 +344,7 @@ static void notrace s390_backup_mcck_info(struct pt_regs *regs)
 
 	sie_page = container_of(sie_block, struct sie_page, sie_block);
 	mcck_backup = &sie_page->mcck_info;
-	mcck_backup->mcic = get_lowcore()->mcck_interruption_code &
-				~(MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE);
+	mcck_backup->mcic = get_lowcore()->mcck_interruption_code & ~MCCK_CODE_NO_GUEST;
 	mcck_backup->ext_damage_code = get_lowcore()->external_damage_code;
 	mcck_backup->failing_storage_address = get_lowcore()->failing_storage_address;
 }

@@ -357,8 +356,6 @@ NOKPROBE_SYMBOL(s390_backup_mcck_info);
 #define ED_STP_ISLAND	6	/* External damage STP island check */
 #define ED_STP_SYNC	7	/* External damage STP sync check */
 
-#define MCCK_CODE_NO_GUEST	(MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE)
-
 /*
  * machine check handler.
  */
arch/s390/kvm/interrupt.c +8 -16
index 009d6a845d59..0d9fbe75dc66 100644
@@ -3108,9 +3108,7 @@ static int set_adapter_int(struct kvm_kernel_irq_routing_entry *e,
 void kvm_s390_reinject_machine_check(struct kvm_vcpu *vcpu,
 				     struct mcck_volatile_info *mcck_info)
 {
-	struct kvm_s390_interrupt_info inti;
 	struct kvm_s390_irq irq = {};
-	struct kvm_s390_mchk_info *mchk;
 	union mci mci;
 	__u64 cr14 = 0;         /* upper bits are not used */
 	int rc;

@@ -3129,20 +3127,14 @@ void kvm_s390_reinject_machine_check(struct kvm_vcpu *vcpu,
 	if (mci.w)
 		cr14 |= CR14_WARNING_SUBMASK;
 
-	mchk = mci.ck ? &inti.mchk : &irq.u.mchk;
-	mchk->cr14 = cr14;
-	mchk->mcic = mcck_info->mcic;
-	mchk->ext_damage_code = mcck_info->ext_damage_code;
-	mchk->failing_storage_address = mcck_info->failing_storage_address;
-	if (mci.ck) {
-		/* Inject the floating machine check */
-		inti.type = KVM_S390_MCHK;
-		rc = __inject_vm(vcpu->kvm, &inti);
-	} else {
-		/* Inject the machine check to specified vcpu */
-		irq.type = KVM_S390_MCHK;
-		rc = kvm_s390_inject_vcpu(vcpu, &irq);
-	}
+	irq.u.mchk.cr14 = cr14;
+	irq.u.mchk.mcic = mcck_info->mcic;
+	irq.u.mchk.ext_damage_code = mcck_info->ext_damage_code;
+	irq.u.mchk.failing_storage_address = mcck_info->failing_storage_address;
+
+	/* Inject the machine check to specified vcpu */
+	irq.type = KVM_S390_MCHK;
+	rc = kvm_s390_inject_vcpu(vcpu, &irq);
 	WARN_ON_ONCE(rc);
 }
maintainer
#1 lore raw

PATCH 1/2 s390: Replace __ASSEMBLY__ with __ASSEMBLER__ in non-uapi headers

From: Thomas Huth <[email protected]>

[ Upstream commit 42398caf16c955251a2dab86f797b76adeb99899 ]

While the GCC and Clang compilers already define __ASSEMBLER__ automatically when compiling assembler code, __ASSEMBLY__ is a macro that only gets defined by the Makefiles in the kernel. This is bad since macros starting with two underscores are names that are reserved by the C language. It can also be very confusing for the developers when switching between userspace and kernelspace coding, or when dealing with uapi headers that rather should use __ASSEMBLER__ instead. So let's now standardize on the __ASSEMBLER__ macro that is provided by the compilers.

This is a completely mechanical patch (done with a simple "sed -i" statement), with some manual fixups done later while rebasing the patch.

Signed-off-by Thomas Huth <[email protected]>
Acked-by Heiko Carstens <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
Signed-off-by Alexander Gordeev <[email protected]>

Stable dependency adaptation for 546dde823a36d7283dcf46127c2f3d093443860f:

Keep only the nmi.h guard conversion from the upstream patch. The other header conversions do not prepare the machine-check fix; several headers and the newer lowcore/alternative infrastructure are absent in 6.6.

Provide get_lowcore() as a macro alias for &S390_lowcore, retaining the fixed-address lowcore semantics of this branch without adding a function. Use that spelling for the three backup accesses and match upstream's failing-storage-address assignment layout. Also zero-initialize the local IRQ structure in kvm_s390_reinject_machine_check() to match the target's context. These changes let the unmodified target patch apply cleanly. The CK filtering and reinjection changes remain in the target commit.

[ sashal: Reduced backport -- upstream 42398caf16c95 touches 33 file(s), this
backport carries 4. Not backported here:
arch/s390/boot/boot.h
arch/s390/include/asm/alternative.h arch/s390/include/asm/asm-const.h
arch/s390/include/asm/cpu.h
arch/s390/include/asm/cpu_mf-insn.h arch/s390/include/asm/ctlreg.h
arch/s390/include/asm/dwarf.h
arch/s390/include/asm/extmem.h
... and 23 more
This note is generated from the file lists only; see the resolution record for the reasoning. ]

Stable-dep-of: 546dde823a36 ("KVM: s390: Fix memory corruption by not reinjecting CK machine checks")

Signed-off-by Sasha Levin <[email protected]>
---
 arch/s390/include/asm/lowcore.h | 3 +++
 arch/s390/include/asm/nmi.h     | 4 ++--
 arch/s390/kernel/nmi.c          | 7 +++----
 arch/s390/kvm/interrupt.c       | 2 +-
 4 files changed, 9 insertions(+), 7 deletions(-)
arch/s390/include/asm/lowcore.h +3 -0
index 8aa1f6530a3e4..c64d744152dfa 100644
@@ -214,6 +214,9 @@ struct lowcore {
 
 #define S390_lowcore (*((struct lowcore *) 0))
 
+/* Lowcore has a fixed address on this kernel. */
+#define get_lowcore() (&S390_lowcore)
+
 extern struct lowcore *lowcore_ptr[];
 
 static inline void set_prefix(__u32 address)
arch/s390/include/asm/nmi.h +2 -2
index af1cd3a6f4060..418bb0aa714cc 100644
@@ -33,7 +33,7 @@
 #define MCCK_CODE_FC_VALID		BIT(63 - 43)
 #define MCCK_CODE_CPU_TIMER_VALID	BIT(63 - 46)
 
-#ifndef __ASSEMBLY__
+#ifndef __ASSEMBLER__
 
 union mci {
 	unsigned long val;

@@ -105,5 +105,5 @@ void s390_handle_mcck(struct pt_regs *regs);
 void __s390_handle_mcck(void);
 int s390_do_machine_check(struct pt_regs *regs);
 
-#endif /* __ASSEMBLY__ */
+#endif /* __ASSEMBLER__ */
 #endif /* _ASM_S390_NMI_H */
arch/s390/kernel/nmi.c +3 -4
index 31cb9b00a36bb..5c9d33ff92fda 100644
@@ -372,11 +372,10 @@ static void notrace s390_backup_mcck_info(struct pt_regs *regs)
 
 	sie_page = container_of(sie_block, struct sie_page, sie_block);
 	mcck_backup = &sie_page->mcck_info;
-	mcck_backup->mcic = S390_lowcore.mcck_interruption_code &
+	mcck_backup->mcic = get_lowcore()->mcck_interruption_code &
 				~(MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE);
-	mcck_backup->ext_damage_code = S390_lowcore.external_damage_code;
-	mcck_backup->failing_storage_address
-			= S390_lowcore.failing_storage_address;
+	mcck_backup->ext_damage_code = get_lowcore()->external_damage_code;
+	mcck_backup->failing_storage_address = get_lowcore()->failing_storage_address;
 }
 NOKPROBE_SYMBOL(s390_backup_mcck_info);
arch/s390/kvm/interrupt.c +1 -1
index a70540697ef34..6be9c79383dd5 100644
@@ -2859,7 +2859,7 @@ void kvm_s390_reinject_machine_check(struct kvm_vcpu *vcpu,
 				     struct mcck_volatile_info *mcck_info)
 {
 	struct kvm_s390_interrupt_info inti;
-	struct kvm_s390_irq irq;
+	struct kvm_s390_irq irq = {};
 	struct kvm_s390_mchk_info *mchk;
 	union mci mci;
 	__u64 cr14 = 0;         /* upper bits are not used */
Signature · 1 line
2.53.0
maintainer
#2 lore raw

PATCH 2/2 KVM: s390: Fix memory corruption by not reinjecting CK machine checks

From: Christian Borntraeger <[email protected]>

[ Upstream commit 546dde823a36d7283dcf46127c2f3d093443860f ]

Channel-subsystem damage machine checks are for the host channel subsystem. The guest channel subsystem is emulated in the userspace VMM. There is no point in forwarding such machine checks into the guest.

This also simplifies the machine check reinjection and avoids kfree of a stack variable as reported by sashiko. There might be still machine checks that have the ck bit set with another bit (like instruction damage), mask out the CK bit in s390_backup_mcck_info(), like the CP and ED bits already are.

Fixes 4d62fcc0b692 ("KVM: s390: Inject machine check into the guest")
Cc [email protected]
Signed-off-by Christian Borntraeger <[email protected]>
Acked-by Heiko Carstens <[email protected]>
Acked-by Claudio Imbrenda <[email protected]>
Signed-off-by Claudio Imbrenda <[email protected]>

Message-ID: <[email protected]>

Signed-off-by Sasha Levin <[email protected]>
---
 arch/s390/include/asm/nmi.h |  3 +++
 arch/s390/kernel/nmi.c      |  5 +----
 arch/s390/kvm/interrupt.c   | 24 ++++++++----------------
 3 files changed, 12 insertions(+), 20 deletions(-)
arch/s390/include/asm/nmi.h +3 -0
index 418bb0aa714cc..418772b9ad664 100644
@@ -22,6 +22,7 @@
 #define MCCK_CODE_SYSTEM_DAMAGE		BIT(63)
 #define MCCK_CODE_EXT_DAMAGE		BIT(63 - 5)
 #define MCCK_CODE_CP			BIT(63 - 9)
+#define MCCK_CODE_CK			BIT(63 - 11)
 #define MCCK_CODE_STG_ERROR		BIT(63 - 16)
 #define MCCK_CODE_STG_KEY_ERROR		BIT(63 - 18)
 #define MCCK_CODE_STG_DEGRAD		BIT(63 - 19)

@@ -33,6 +34,8 @@
 #define MCCK_CODE_FC_VALID		BIT(63 - 43)
 #define MCCK_CODE_CPU_TIMER_VALID	BIT(63 - 46)
 
+#define MCCK_CODE_NO_GUEST	(MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE | MCCK_CODE_CK)
+
 #ifndef __ASSEMBLER__
 
 union mci {
arch/s390/kernel/nmi.c +1 -4
index 5c9d33ff92fda..bf05bf3a54338 100644
@@ -372,8 +372,7 @@ static void notrace s390_backup_mcck_info(struct pt_regs *regs)
 
 	sie_page = container_of(sie_block, struct sie_page, sie_block);
 	mcck_backup = &sie_page->mcck_info;
-	mcck_backup->mcic = get_lowcore()->mcck_interruption_code &
-				~(MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE);
+	mcck_backup->mcic = get_lowcore()->mcck_interruption_code & ~MCCK_CODE_NO_GUEST;
 	mcck_backup->ext_damage_code = get_lowcore()->external_damage_code;
 	mcck_backup->failing_storage_address = get_lowcore()->failing_storage_address;
 }

@@ -385,8 +384,6 @@ NOKPROBE_SYMBOL(s390_backup_mcck_info);
 #define ED_STP_ISLAND	6	/* External damage STP island check */
 #define ED_STP_SYNC	7	/* External damage STP sync check */
 
-#define MCCK_CODE_NO_GUEST	(MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE)
-
 /*
  * machine check handler.
  */
arch/s390/kvm/interrupt.c +8 -16
index 6be9c79383dd5..cd5f387c9b76b 100644
@@ -2858,9 +2858,7 @@ static int set_adapter_int(struct kvm_kernel_irq_routing_entry *e,
 void kvm_s390_reinject_machine_check(struct kvm_vcpu *vcpu,
 				     struct mcck_volatile_info *mcck_info)
 {
-	struct kvm_s390_interrupt_info inti;
 	struct kvm_s390_irq irq = {};
-	struct kvm_s390_mchk_info *mchk;
 	union mci mci;
 	__u64 cr14 = 0;         /* upper bits are not used */
 	int rc;

@@ -2873,20 +2871,14 @@ void kvm_s390_reinject_machine_check(struct kvm_vcpu *vcpu,
 	if (mci.w)
 		cr14 |= CR14_WARNING_SUBMASK;
 
-	mchk = mci.ck ? &inti.mchk : &irq.u.mchk;
-	mchk->cr14 = cr14;
-	mchk->mcic = mcck_info->mcic;
-	mchk->ext_damage_code = mcck_info->ext_damage_code;
-	mchk->failing_storage_address = mcck_info->failing_storage_address;
-	if (mci.ck) {
-		/* Inject the floating machine check */
-		inti.type = KVM_S390_MCHK;
-		rc = __inject_vm(vcpu->kvm, &inti);
-	} else {
-		/* Inject the machine check to specified vcpu */
-		irq.type = KVM_S390_MCHK;
-		rc = kvm_s390_inject_vcpu(vcpu, &irq);
-	}
+	irq.u.mchk.cr14 = cr14;
+	irq.u.mchk.mcic = mcck_info->mcic;
+	irq.u.mchk.ext_damage_code = mcck_info->ext_damage_code;
+	irq.u.mchk.failing_storage_address = mcck_info->failing_storage_address;
+
+	/* Inject the machine check to specified vcpu */
+	irq.type = KVM_S390_MCHK;
+	rc = kvm_s390_inject_vcpu(vcpu, &irq);
 	WARN_ON_ONCE(rc);
 }
Signature · 1 line
2.53.0