From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794273711; b=HTd+UDK7sanzzmYRZy3dyRQHj44AvXt4neyXsxJ5XiMuTaj6uD5OBsxjWSum6mjFrmqd /I0XVJE223iPLUzSN7h3rvdCTIvNk3wJFmNqbrJ+hiDdgm9D9lBD1zLup82ce84iXLpSa TvvXZOexyDNY/y2l21MXIN9UOtiSuP2v+2KnjIt9yDCmIqiIHQxVmNvOku8NvE19d7Vdt trSQotxN3FOffc+KPzTEm9uX2JBOBhsCLVmnFmhgzMFMSDgUJnOcOZXOa9kzLxcuo3s96 XSPg/+NeDdp6yMSiSYbP0acCz33W7e33AQq8vVaQQxSTjTR9t1atWZQW6OThFM/VavA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794273711; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=N8p5sXyeIAWBzF7nl86pU4ANlw/KMVAXvR6Rr4S7/+Q=; b=ikR5WPg+aUgAaw1CdU+Odb2hNGu1NSA1S9HvgvEru1vYp36BJ/NGbjzWGwHDcMSJ4sxc Wk7CWX/UuCWbcVjP+lqe9yiFZYsfguty1cCrPU5iDPfkziNic0eNpGREVYZG05k8kcKEk DArZ80TUYQmSk66GWFpIvsJd9FgLVYdyKMdbKIxFquYCSjhaYJDBpwjeHCF5NwpHz1OVL Y8Pd2GatHQlS4B5tZV6Jy4G3kXjoIsa9g/tcYHt5wpIXAFR6NtoQYjAOV0WUPOEvtR5EY kIynBZfsChp9+Nh2LqS5WnQvQjWtEqyXzXue/o5FQ96izKCbia0qf2CVsGTbJiX/QZg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=HqOz+gv5; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A5836606A334 for ; Tue, 10 Nov 2026 01:21:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=HqOz+gv5 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9575D1F008A2; Tue, 10 Nov 2026 01:21:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794273710; bh=N8p5sXyeIAWBzF7nl86pU4ANlw/KMVAXvR6Rr4S7/+Q=; h=From:To:Cc:Subject:Date; b=HqOz+gv5ppJyT7vkMhcaSIVjdIqR6sAC2TslzKg2wRvNOMjkquOsO5qIrH1DCR+IL 3+tL2Wg+gMq1xqn4c43QsLrOuuzEvL03+qJjTWHjICrHYnNTaBYhy7xA56CaZiP0br LRJH16Iujnyvou6fDnwbeQ4aFQ8LjMh/hRWP06H7deX983tNOMDONA09fuVZHTql0y 6Tr9k3c0pfxC6dBP/JfmQYr1tJDLCRCRdjQqg8yYnG4b6mUIDolQFI0Pua+tVAd6jX U/0iEvOGKSw0VPpFmYURDUusicSHP9j7SgPn1QwocNhmATH5BEslIkctcqVJsibbly oSWhgHywVXMQg== From: Sasha Levin To: seanjc@google.com, morbo@google.com, fane@google.com, pbonzini@redhat.com Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] KVM: nSVM: Check validity of vmcs01 save area copied from SMRAM on RSM" failed to apply to 5.15-stable tree Date: Mon, 9 Nov 2026 20:21:48 -0500 Message-ID: <20261109202148-failed-5.15-053621535f01@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.15-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 . 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-5.15.y git checkout FETCH_HEAD git cherry-pick -x 053621535f014085c935879582dd3b65964a0dce # git commit -s git send-email --to '' --in-reply-to '20261109202148-failed-5.15-053621535f01@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 053621535f014085c935879582dd3b65964a0dce Mon Sep 17 00:00:00 2001 From: Sean Christopherson 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: 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 ---[ end trace ]--- Fixes: 37be407b2ce8 ("KVM: nSVM: Fix L1 state corruption upon return from SMM") Cc: stable@vger.kernel.org Reported-by: Bill Wendling Reported-by: Stefan Teodorescu Tested-by: Stefan Teodorescu Signed-off-by: Sean Christopherson Message-ID: <20261022021046.295001-1-seanjc@google.com> Signed-off-by: Paolo Bonzini --- 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