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KVM: x86: work around leak of uninitialized stack contents (CVE-2019-7222) 

commit 353c0956a6 upstream.

Bugzilla: 1671930

Emulation of certain instructions (VMXON, VMCLEAR, VMPTRLD, VMWRITE with
memory operand, INVEPT, INVVPID) can incorrectly inject a page fault
when passed an operand that points to an MMIO address.  The page fault
will use uninitialized kernel stack memory as the CR2 and error code.

The right behavior would be to abort the VM with a KVM_EXIT_INTERNAL_ERROR
exit to userspace; however, it is not an easy fix, so for now just
ensure that the error code and CR2 are zero.

Embargoed until Feb 7th 2019.

Reported-by: Felix Wilhelm <fwilhelm@google.com>
Cc: stable@kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Paolo Bonzini 2019-01-29 18:41:16 +01:00 committed by Greg Kroah-Hartman
parent d26358590b
commit f5c61e4f6b
1 changed files with 7 additions and 0 deletions
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7
arch/x86/kvm/x86.c
View File

@ -4513,6 +4513,13 @@ int kvm_read_guest_virt(struct kvm_vcpu *vcpu,
{
u32 access = (kvm_x86_ops->get_cpl(vcpu) == 3) ? PFERR_USER_MASK : 0;
/*
* FIXME: this should call handle_emulation_failure if X86EMUL_IO_NEEDED
* is returned, but our callers are not ready for that and they blindly
* call kvm_inject_page_fault. Ensure that they at least do not leak
* uninitialized kernel stack memory into cr2 and error code.
*/
memset(exception, 0, sizeof(*exception));
return kvm_read_guest_virt_helper(addr, val, bytes, vcpu, access,
exception);
}