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authorMarcelo Tosatti <mtosatti@redhat.com>2009-04-16 08:30:44 -0300
committerAvi Kivity <avi@redhat.com>2009-06-10 11:48:43 +0300
commit59839dfff5eabca01cc4e20b45797a60a80af8cb (patch)
treee6818499bdfa84dea4634354288ed50c677aaec8
parentc6b60c6921381130e5288b19f5fdf81152230b37 (diff)
KVM: x86: check for cr3 validity in ioctl_set_sregs
Matt T. Yourst notes that kvm_arch_vcpu_ioctl_set_sregs lacks validity checking for the new cr3 value: "Userspace callers of KVM_SET_SREGS can pass a bogus value of cr3 to the kernel. This will trigger a NULL pointer access in gfn_to_rmap() when userspace next tries to call KVM_RUN on the affected VCPU and kvm attempts to activate the new non-existent page table root. This happens since kvm only validates that cr3 points to a valid guest physical memory page when code *inside* the guest sets cr3. However, kvm currently trusts the userspace caller (e.g. QEMU) on the host machine to always supply a valid page table root, rather than properly validating it along with the rest of the reloaded guest state." http://sourceforge.net/tracker/?func=detail&atid=893831&aid=2687641&group_id=180599 Check for a valid cr3 address in kvm_arch_vcpu_ioctl_set_sregs, triple fault in case of failure. Cc: stable@kernel.org Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com>
-rw-r--r--arch/x86/kvm/x86.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ffbb2c818d7..2bad49b535c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3993,7 +3993,13 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
vcpu->arch.cr2 = sregs->cr2;
mmu_reset_needed |= vcpu->arch.cr3 != sregs->cr3;
- vcpu->arch.cr3 = sregs->cr3;
+
+ down_read(&vcpu->kvm->slots_lock);
+ if (gfn_to_memslot(vcpu->kvm, sregs->cr3 >> PAGE_SHIFT))
+ vcpu->arch.cr3 = sregs->cr3;
+ else
+ set_bit(KVM_REQ_TRIPLE_FAULT, &vcpu->requests);
+ up_read(&vcpu->kvm->slots_lock);
kvm_set_cr8(vcpu, sregs->cr8);