From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
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,
Ben Gardon <bgardon@google.com>,
Brijesh Singh <brijesh.singh@amd.com>,
Tom Lendacky <thomas.lendacky@amd.com>
Subject: [PATCH 15/15] KVM: x86/mmu: WARN on NULL pae_root and bad shadow root level
Date: Tue, 2 Mar 2021 10:45:40 -0800 [thread overview]
Message-ID: <20210302184540.2829328-16-seanjc@google.com> (raw)
In-Reply-To: <20210302184540.2829328-1-seanjc@google.com>
WARN if KVM is about to derference a NULL pae_root when loading an MMU,
and convert the BUG() on a bad shadow_root_level into a WARN (now that
errors are handled cleanly). With nested NPT, botching the level and
sending KVM down the wrong path is all too easy, and the on-demand
allocation of pae_root means bugs crash the host. Obviously, KVM could
unconditionally allocate pae_root, but that's arguably a worse failure
mode as it would potentially corrupt the guest instead of crashing it.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/mmu/mmu.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 34eeb39ee0f9..35f89bb1f205 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3247,6 +3247,9 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
true);
vcpu->arch.mmu->root_hpa = root;
} else if (shadow_root_level == PT32E_ROOT_LEVEL) {
+ if (WARN_ON_ONCE(!vcpu->arch.mmu->pae_root))
+ return -EIO;
+
for (i = 0; i < 4; ++i) {
WARN_ON_ONCE(vcpu->arch.mmu->pae_root[i]);
@@ -3256,8 +3259,10 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
shadow_me_mask;
}
vcpu->arch.mmu->root_hpa = __pa(vcpu->arch.mmu->pae_root);
- } else
- BUG();
+ } else {
+ WARN_ONCE(1, "Bad TDP root level = %d\n", shadow_root_level);
+ return -EIO;
+ }
/* root_pgd is ignored for direct MMUs. */
vcpu->arch.mmu->root_pgd = 0;
@@ -3340,6 +3345,8 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
vcpu->arch.mmu->lm_root = lm_root;
lm_root[0] = __pa(vcpu->arch.mmu->pae_root) | pm_mask;
+ } else if (WARN_ON_ONCE(!vcpu->arch.mmu->pae_root)) {
+ return -EIO;
}
for (i = 0; i < 4; ++i) {
--
2.30.1.766.gb4fecdf3b7-goog
prev parent reply other threads:[~2021-03-02 21:48 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-02 18:45 [PATCH 00/15] KVM: x86/mmu: Lots of bug fixes Sean Christopherson
2021-03-02 18:45 ` [PATCH 01/15] KVM: nSVM: Set the shadow root level to the TDP level for nested NPT Sean Christopherson
2021-03-02 18:45 ` [PATCH 02/15] KVM: x86/mmu: Alloc page for PDPTEs when shadowing 32-bit NPT with 64-bit Sean Christopherson
2021-03-03 17:28 ` Ben Gardon
2021-03-02 18:45 ` [PATCH 03/15] KVM: x86/mmu: Ensure MMU pages are available when allocating roots Sean Christopherson
2021-03-03 0:21 ` Ben Gardon
2021-03-03 16:46 ` Sean Christopherson
2021-03-02 18:45 ` [PATCH 04/15] KVM: x86/mmu: Allocate the lm_root before allocating PAE roots Sean Christopherson
2021-03-02 18:45 ` [PATCH 05/15] KVM: x86/mmu: Check PDPTRs " Sean Christopherson
2021-03-02 18:45 ` [PATCH 06/15] KVM: x86/mmu: Fix and unconditionally enable WARNs to detect PAE leaks Sean Christopherson
2021-03-02 18:45 ` [PATCH 07/15] KVM: x86/mmu: Use '0' as the one and only value for an invalid PAE root Sean Christopherson
2021-03-02 18:45 ` [PATCH 08/15] KVM: x86/mmu: Set the C-bit in the PDPTRs and LM pseudo-PDPTRs Sean Christopherson
2021-03-02 18:45 ` [PATCH 09/15] KVM: x86/mmu: Mark the PAE roots as decrypted for shadow paging Sean Christopherson
2021-03-02 18:45 ` [PATCH 10/15] KVM: SVM: Don't strip the C-bit from CR2 on #PF interception Sean Christopherson
2021-03-02 18:45 ` [PATCH 11/15] KVM: nVMX: Defer the MMU reload to the normal path on an EPTP switch Sean Christopherson
2021-03-02 18:45 ` [PATCH 12/15] KVM: x86: Defer the MMU unload to the normal path on an global INVPCID Sean Christopherson
2021-03-02 18:45 ` [PATCH 13/15] KVM: x86/mmu: Unexport MMU load/unload functions Sean Christopherson
2021-03-02 18:45 ` [PATCH 14/15] KVM: x86/mmu: Sync roots after MMU load iff load as successful Sean Christopherson
2021-03-02 18:45 ` Sean Christopherson [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210302184540.2829328-16-seanjc@google.com \
--to=seanjc@google.com \
--cc=bgardon@google.com \
--cc=brijesh.singh@amd.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=thomas.lendacky@amd.com \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).