From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
syzbot+fb0b6a7e8713aeb0319c@syzkaller.appspotmail.com
Subject: Re: [PATCH 1/9] KVM: x86: Immediately reset the MMU context when the SMM flag is cleared
Date: Thu, 10 Jun 2021 15:19:07 +0200 [thread overview]
Message-ID: <eb0b94d4-9edf-6ef6-25f9-27a3e407f60b@redhat.com> (raw)
In-Reply-To: <20210609185619.992058-2-seanjc@google.com>
On 09/06/21 20:56, Sean Christopherson wrote:
> Immediately reset the MMU context when the vCPU's SMM flag is cleared so
> that the SMM flag in the MMU role is always synchronized with the vCPU's
> flag. If RSM fails (which isn't correctly emulated), KVM will bail
> without calling post_leave_smm() and leave the MMU in a bad state.
>
> The bad MMU role can lead to a NULL pointer dereference when grabbing a
> shadow page's rmap for a page fault as the initial lookups for the gfn
> will happen with the vCPU's SMM flag (=0), whereas the rmap lookup will
> use the shadow page's SMM flag, which comes from the MMU (=1). SMM has
> an entirely different set of memslots, and so the initial lookup can find
> a memslot (SMM=0) and then explode on the rmap memslot lookup (SMM=1).
>
> general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> CPU: 1 PID: 8410 Comm: syz-executor382 Not tainted 5.13.0-rc5-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:__gfn_to_rmap arch/x86/kvm/mmu/mmu.c:935 [inline]
> RIP: 0010:gfn_to_rmap+0x2b0/0x4d0 arch/x86/kvm/mmu/mmu.c:947
> Code: <42> 80 3c 20 00 74 08 4c 89 ff e8 f1 79 a9 00 4c 89 fb 4d 8b 37 44
> RSP: 0018:ffffc90000ffef98 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: ffff888015b9f414 RCX: ffff888019669c40
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
> RBP: 0000000000000001 R08: ffffffff811d9cdb R09: ffffed10065a6002
> R10: ffffed10065a6002 R11: 0000000000000000 R12: dffffc0000000000
> R13: 0000000000000003 R14: 0000000000000001 R15: 0000000000000000
> FS: 000000000124b300(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000000 CR3: 0000000028e31000 CR4: 00000000001526e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> rmap_add arch/x86/kvm/mmu/mmu.c:965 [inline]
> mmu_set_spte+0x862/0xe60 arch/x86/kvm/mmu/mmu.c:2604
> __direct_map arch/x86/kvm/mmu/mmu.c:2862 [inline]
> direct_page_fault+0x1f74/0x2b70 arch/x86/kvm/mmu/mmu.c:3769
> kvm_mmu_do_page_fault arch/x86/kvm/mmu.h:124 [inline]
> kvm_mmu_page_fault+0x199/0x1440 arch/x86/kvm/mmu/mmu.c:5065
> vmx_handle_exit+0x26/0x160 arch/x86/kvm/vmx/vmx.c:6122
> vcpu_enter_guest+0x3bdd/0x9630 arch/x86/kvm/x86.c:9428
> vcpu_run+0x416/0xc20 arch/x86/kvm/x86.c:9494
> kvm_arch_vcpu_ioctl_run+0x4e8/0xa40 arch/x86/kvm/x86.c:9722
> kvm_vcpu_ioctl+0x70f/0xbb0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3460
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:1069 [inline]
> __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:1055
> do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x440ce9
>
> Reported-by: syzbot+fb0b6a7e8713aeb0319c@syzkaller.appspotmail.com
> Fixes: 9ec19493fb86 ("KVM: x86: clear SMM flags before loading state while leaving SMM")
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/x86/kvm/x86.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 9dd23bdfc6cc..54d212fe9b15 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7106,7 +7106,10 @@ static unsigned emulator_get_hflags(struct x86_emulate_ctxt *ctxt)
>
> static void emulator_set_hflags(struct x86_emulate_ctxt *ctxt, unsigned emul_flags)
> {
> - emul_to_vcpu(ctxt)->arch.hflags = emul_flags;
> + struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
> +
> + vcpu->arch.hflags = emul_flags;
> + kvm_mmu_reset_context(vcpu);
> }
>
> static int emulator_pre_leave_smm(struct x86_emulate_ctxt *ctxt,
>
Queued for kvm/master, thanks.
Paolo
next prev parent reply other threads:[~2021-06-10 13:19 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-09 18:56 [PATCH 0/9] KVM: x86: Fix NULL pointer #GP due to RSM bug Sean Christopherson
2021-06-09 18:56 ` [PATCH 1/9] KVM: x86: Immediately reset the MMU context when the SMM flag is cleared Sean Christopherson
2021-06-10 13:19 ` Paolo Bonzini [this message]
2021-06-09 18:56 ` [PATCH 2/9] KVM: x86: Emulate triple fault shutdown if RSM emulation fails Sean Christopherson
2021-06-10 8:26 ` Vitaly Kuznetsov
2021-06-10 13:29 ` Paolo Bonzini
2021-06-10 15:28 ` Sean Christopherson
2021-06-10 15:30 ` Sean Christopherson
2021-06-11 11:42 ` Vitaly Kuznetsov
2021-06-10 13:23 ` Paolo Bonzini
2021-06-09 18:56 ` [PATCH 3/9] KVM: x86: Replace .set_hflags() with dedicated .exiting_smm() helper Sean Christopherson
2021-06-09 18:56 ` [PATCH 4/9] KVM: x86: Invoke kvm_smm_changed() immediately after clearing SMM flag Sean Christopherson
2021-06-09 18:56 ` [PATCH 5/9] KVM: x86: Move (most) SMM hflags modifications into kvm_smm_changed() Sean Christopherson
2021-06-09 18:56 ` [PATCH 6/9] KVM: x86: Move "entering SMM" tracepoint " Sean Christopherson
2021-06-09 18:56 ` [PATCH 7/9] KVM: x86: Rename SMM tracepoint to make it reflect reality Sean Christopherson
2021-06-09 18:56 ` [PATCH 8/9] KVM: x86: Drop .post_leave_smm(), i.e. the manual post-RSM MMU reset Sean Christopherson
2021-06-09 18:56 ` [PATCH 9/9] KVM: x86: Drop "pre_" from enter/leave_smm() helpers Sean Christopherson
2021-06-10 13:28 ` [PATCH 0/9] KVM: x86: Fix NULL pointer #GP due to RSM bug Paolo Bonzini
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