* FAILED: patch "[PATCH] KVM: nSVM: Check validity of vmcs01 save area copied from SMRAM on RSM" failed to apply to 6.12-stable tree
@ 2026-11-10 1:07 Sasha Levin
2026-11-11 17:19 ` [PATCH 6.12.y] KVM: nSVM: Check validity of vmcs01 save area copied from SMRAM on RSM Sasha Levin
0 siblings, 1 reply; 2+ messages in thread
From: Sasha Levin @ 2026-11-10 1:07 UTC (permalink / raw)
To: seanjc, morbo, fane, pbonzini; +Cc: stable
The patch below does not apply to the 6.12-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 <stable@vger.kernel.org>.
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-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 053621535f014085c935879582dd3b65964a0dce
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261109200735-failed-6.12-053621535f01@kernel.org' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'
Thanks,
Sasha
------------------ original commit in Linus's tree ------------------
From 053621535f014085c935879582dd3b65964a0dce Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Wed, 21 Oct 2026 19:10:46 -0700
Subject: [PATCH] KVM: nSVM: Check validity of vmcs01 save area copied from
SMRAM on RSM
When doing RSM to L2, validate L1's state after copying it back into vmcb01
from SMRAM, as SMRAM is carved out of guest memory, i.e. is writable by the
guest. Failure to validate L1's state is especially problematic for inputs
to MMU context, as KVM can end up with impossible CR4 vs. EFER state. E.g.
without the recent hardening FNAME(walk_addr_generic), a guest can trigger:
------------[ cut here ]------------
UBSAN: array-index-out-of-bounds in arch/x86/kvm/mmu/paging_tmpl.h:435:15
index 3 is out of range for type 'u32 [2]'
CPU: 3 UID: 0 PID: 92 Comm: CPU 1/KVM Not tainted 7.3.0-rc1 #2 PREEMPT(lazy)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x5f/0x90
dump_stack+0x10/0x18
ubsan_epilogue+0x9/0x39
__ubsan_handle_out_of_bounds.cold+0x50/0x55
paging32_walk_addr_generic+0x889/0x970
paging32_page_fault+0x79/0xa60
kvm_mmu_do_page_fault+0x125/0x270
kvm_mmu_page_fault+0x88/0x7b0
npf_interception+0xc8/0x220 [kvm_amd]
svm_invoke_exit_handler+0x16d/0x1d0 [kvm_amd]
svm_handle_exit+0xb7/0x160 [kvm_amd]
vcpu_enter_guest+0x428/0x16a0
kvm_arch_vcpu_ioctl_run+0x479/0x920
kvm_vcpu_ioctl+0x316/0xb00
__x64_sys_ioctl+0xa3/0x100
x64_sys_call+0x281/0x23d0
do_syscall_64+0xba/0x550
entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x79bb30deb04b
</TASK>
---[ end trace ]---
Fixes: 37be407b2ce8 ("KVM: nSVM: Fix L1 state corruption upon return from SMM")
Cc: stable@vger.kernel.org
Reported-by: Bill Wendling <morbo@google.com>
Reported-by: Stefan Teodorescu <fane@google.com>
Tested-by: Stefan Teodorescu <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20261022021046.295001-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/svm/nested.c | 23 ++++++++++++++++-------
arch/x86/kvm/svm/svm.c | 2 ++
arch/x86/kvm/svm/svm.h | 2 ++
3 files changed, 20 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index af0ef678433d7..07554089ec05b 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1889,6 +1889,21 @@ static void nested_copy_vmcb_cache_to_control(struct vmcb_control_area *dst,
/* 'clean' and 'hv_enlightenments' are not changed by KVM */
}
+bool nested_svm_check_vmcb01_save(struct kvm_vcpu *vcpu,
+ struct vmcb_save_area *save)
+{
+ struct vmcb_save_area_cached save_cached;
+
+ if (!(save->cr0 & X86_CR0_PG) ||
+ !(save->cr0 & X86_CR0_PE) ||
+ (save->rflags & X86_EFLAGS_VM) ||
+ ((save->efer & EFER_LMA) && !(save->efer & EFER_LME)))
+ return false;
+
+ __nested_copy_vmcb_save_to_cache(&save_cached, save);
+ return nested_vmcb_check_save(vcpu, &save_cached, false);
+}
+
static int svm_get_nested_state(struct kvm_vcpu *vcpu,
struct kvm_nested_state __user *user_kvm_nested_state,
u32 user_data_size)
@@ -1968,7 +1983,6 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
&user_kvm_nested_state->data.svm[0];
struct vmcb_control_area *ctl;
struct vmcb_save_area *save;
- struct vmcb_save_area_cached save_cached;
struct vmcb_ctrl_area_cached ctl_cached;
bool use_separate_l2_pat;
unsigned long cr0;
@@ -2040,12 +2054,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
* KVM_GET_NESTED_STATE, and (b) it is not loaded at emulated
* #VMEXIT.
*/
- __nested_copy_vmcb_save_to_cache(&save_cached, save);
- if (!(save->cr0 & X86_CR0_PG) ||
- !(save->cr0 & X86_CR0_PE) ||
- (save->rflags & X86_EFLAGS_VM) ||
- ((save->efer & EFER_LMA) && !(save->efer & EFER_LME)) ||
- !nested_vmcb_check_save(vcpu, &save_cached, false))
+ if (!nested_svm_check_vmcb01_save(vcpu, save))
goto out_free;
/*
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 487897ef11dd6..581bc3a23c95a 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -5219,6 +5219,8 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const union kvm_smram *smram)
*/
svm_copy_vmrun_state(vcpu, &svm->vmcb01.ptr->save, m_save.map.hva + 0x400);
+ if (!nested_svm_check_vmcb01_save(vcpu, &svm->vmcb01.ptr->save))
+ return 1;
/*
* Enter the nested guest now
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 4b0b2ee13a3a5..b9f7786bf17ce 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -911,6 +911,8 @@ void nested_copy_vmcb_control_to_cache(struct vcpu_svm *svm,
void nested_copy_vmcb_save_to_cache(struct vcpu_svm *svm,
struct vmcb_save_area *save);
void nested_sync_control_from_vmcb02(struct vcpu_svm *svm);
+bool nested_svm_check_vmcb01_save(struct kvm_vcpu *vcpu,
+ struct vmcb_save_area *save);
void svm_switch_vmcb(struct vcpu_svm *svm, struct kvm_vmcb_info *target_vmcb);
--
2.53.0
^ permalink raw reply related [flat|nested] 2+ messages in thread* [PATCH 6.12.y] KVM: nSVM: Check validity of vmcs01 save area copied from SMRAM on RSM
2026-11-10 1:07 FAILED: patch "[PATCH] KVM: nSVM: Check validity of vmcs01 save area copied from SMRAM on RSM" failed to apply to 6.12-stable tree Sasha Levin
@ 2026-11-11 17:19 ` Sasha Levin
0 siblings, 0 replies; 2+ messages in thread
From: Sasha Levin @ 2026-11-11 17:19 UTC (permalink / raw)
To: stable
Cc: Sean Christopherson, Bill Wendling, Stefan Teodorescu,
Paolo Bonzini, Sasha Levin
From: Sean Christopherson <seanjc@google.com>
[ Upstream commit 053621535f014085c935879582dd3b65964a0dce ]
When doing RSM to L2, validate L1's state after copying it back into vmcb01
from SMRAM, as SMRAM is carved out of guest memory, i.e. is writable by the
guest. Failure to validate L1's state is especially problematic for inputs
to MMU context, as KVM can end up with impossible CR4 vs. EFER state. E.g.
without the recent hardening FNAME(walk_addr_generic), a guest can trigger:
------------[ cut here ]------------
UBSAN: array-index-out-of-bounds in arch/x86/kvm/mmu/paging_tmpl.h:435:15
index 3 is out of range for type 'u32 [2]'
CPU: 3 UID: 0 PID: 92 Comm: CPU 1/KVM Not tainted 7.3.0-rc1 #2 PREEMPT(lazy)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x5f/0x90
dump_stack+0x10/0x18
ubsan_epilogue+0x9/0x39
__ubsan_handle_out_of_bounds.cold+0x50/0x55
paging32_walk_addr_generic+0x889/0x970
paging32_page_fault+0x79/0xa60
kvm_mmu_do_page_fault+0x125/0x270
kvm_mmu_page_fault+0x88/0x7b0
npf_interception+0xc8/0x220 [kvm_amd]
svm_invoke_exit_handler+0x16d/0x1d0 [kvm_amd]
svm_handle_exit+0xb7/0x160 [kvm_amd]
vcpu_enter_guest+0x428/0x16a0
kvm_arch_vcpu_ioctl_run+0x479/0x920
kvm_vcpu_ioctl+0x316/0xb00
__x64_sys_ioctl+0xa3/0x100
x64_sys_call+0x281/0x23d0
do_syscall_64+0xba/0x550
entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x79bb30deb04b
</TASK>
---[ end trace ]---
Fixes: 37be407b2ce8 ("KVM: nSVM: Fix L1 state corruption upon return from SMM")
Cc: stable@vger.kernel.org
Reported-by: Bill Wendling <morbo@google.com>
Reported-by: Stefan Teodorescu <fane@google.com>
Tested-by: Stefan Teodorescu <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20261022021046.295001-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[ sashal: adapted validation to __nested_vmcb_check_save() with failures routed through the existing unmap_save cleanup ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kvm/svm/nested.c | 23 ++++++++++++++++-------
arch/x86/kvm/svm/svm.c | 2 ++
arch/x86/kvm/svm/svm.h | 2 ++
3 files changed, 20 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 3c9c20d7855fe..670a5d57f33da 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1613,6 +1613,21 @@ static void nested_copy_vmcb_cache_to_control(struct vmcb_control_area *dst,
/* 'clean' and 'hv_enlightenments' are not changed by KVM */
}
+bool nested_svm_check_vmcb01_save(struct kvm_vcpu *vcpu,
+ struct vmcb_save_area *save)
+{
+ struct vmcb_save_area_cached save_cached;
+
+ if (!(save->cr0 & X86_CR0_PG) ||
+ !(save->cr0 & X86_CR0_PE) ||
+ (save->rflags & X86_EFLAGS_VM) ||
+ ((save->efer & EFER_LMA) && !(save->efer & EFER_LME)))
+ return false;
+
+ __nested_copy_vmcb_save_to_cache(&save_cached, save);
+ return __nested_vmcb_check_save(vcpu, &save_cached);
+}
+
static int svm_get_nested_state(struct kvm_vcpu *vcpu,
struct kvm_nested_state __user *user_kvm_nested_state,
u32 user_data_size)
@@ -1689,7 +1704,6 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
&user_kvm_nested_state->data.svm[0];
struct vmcb_control_area *ctl;
struct vmcb_save_area *save;
- struct vmcb_save_area_cached save_cached;
struct vmcb_ctrl_area_cached ctl_cached;
unsigned long cr0;
int ret;
@@ -1759,12 +1773,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
* Validate host state saved from before VMRUN (see
* nested_svm_check_permissions).
*/
- __nested_copy_vmcb_save_to_cache(&save_cached, save);
- if (!(save->cr0 & X86_CR0_PG) ||
- !(save->cr0 & X86_CR0_PE) ||
- (save->rflags & X86_EFLAGS_VM) ||
- ((save->efer & EFER_LMA) && !(save->efer & EFER_LME)) ||
- !__nested_vmcb_check_save(vcpu, &save_cached))
+ if (!nested_svm_check_vmcb01_save(vcpu, save))
goto out_free;
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index df325d0864819..2796368f231d3 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4960,6 +4960,8 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const union kvm_smram *smram)
*/
svm_copy_vmrun_state(&svm->vmcb01.ptr->save, map_save.hva + 0x400);
+ if (!nested_svm_check_vmcb01_save(vcpu, &svm->vmcb01.ptr->save))
+ goto unmap_save;
/*
* Enter the nested guest now
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 511fadfb055f6..a3724e867a4c9 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -689,6 +689,8 @@ void nested_copy_vmcb_save_to_cache(struct vcpu_svm *svm,
struct vmcb_save_area *save);
void nested_sync_control_from_vmcb02(struct vcpu_svm *svm);
void nested_vmcb02_compute_g_pat(struct vcpu_svm *svm);
+bool nested_svm_check_vmcb01_save(struct kvm_vcpu *vcpu,
+ struct vmcb_save_area *save);
void svm_switch_vmcb(struct vcpu_svm *svm, struct kvm_vmcb_info *target_vmcb);
extern struct kvm_x86_nested_ops svm_nested_ops;
--
2.53.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
end of thread, other threads:[~2026-11-11 17:19 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-11-10 1:07 FAILED: patch "[PATCH] KVM: nSVM: Check validity of vmcs01 save area copied from SMRAM on RSM" failed to apply to 6.12-stable tree Sasha Levin
2026-11-11 17:19 ` [PATCH 6.12.y] KVM: nSVM: Check validity of vmcs01 save area copied from SMRAM on RSM Sasha Levin
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox