From: Tom Roeder <tmroeder@google.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Liran Alon" <liran.alon@oracle.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"H . Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org,
syzbot+ded1696f6b50b615b630@syzkaller.appspotmail.com
Subject: Re: [RFC PATCH] kvm: x86/vmx: Use kzalloc for cached_vmcs12
Date: Wed, 23 Jan 2019 10:33:22 -0800 [thread overview]
Message-ID: <20190123183322.GB160275@google.com> (raw)
In-Reply-To: <20190115175111.GB68985@google.com>
On Tue, Jan 15, 2019 at 09:51:11AM -0800, Tom Roeder wrote:
> On Mon, Jan 14, 2019 at 06:43:04PM -0800, Sean Christopherson wrote:
> > On Mon, Jan 14, 2019 at 03:47:28PM -0800, Tom Roeder wrote:
> > > This changes the allocation of cached_vmcs12 to use kzalloc instead of
> > > kmalloc. This removes the information leak found by Syzkaller (see
> > > Reported-by) in this case and prevents similar leaks from happening
> > > based on cached_vmcs12.
> >
> > Is the leak specific to vmx_set_nested_state(), e.g. can we zero out
> > the memory if copy_from_user() fails instead of taking the hit on every
> > allocation?
>
> I don't know if the leak is specific to vmx_set_nested_state.
I've looked at the code more now, and it looks to me like there might be
other cases where the memory could leak. But I don't know enough of the
flows to be sure. The enter_vmx_operation function is called in
handle_vmon, and no data is copied from the guest immediately after
that. So, it depends on what happens after VMXON.
Even in vmx_set_nested_state, there are about 30 lines of code in
between enter_vmx_operation and copy_from_user, and there are a couple
of cases that cause vmx_set_nested_state to return with an error. So if
we want to fix this by handling all the error paths, I think it might be
cleanest to convert vmx_set_nested_state to use goto error handling,
since that would allow us to clear the allocated memory in one place.
What do you think?
next prev parent reply other threads:[~2019-01-23 18:33 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-07 1:38 KMSAN: kernel-infoleak in kvm_vcpu_write_guest_page syzbot
2018-11-07 12:10 ` Alexander Potapenko
2018-11-07 12:47 ` Paolo Bonzini
2018-11-07 12:58 ` Liran Alon
2018-11-07 13:37 ` Paolo Bonzini
2019-01-14 23:47 ` [RFC PATCH] kvm: x86/vmx: Use kzalloc for cached_vmcs12 Tom Roeder
2019-01-15 0:03 ` Jim Mattson
2019-01-15 2:43 ` Sean Christopherson
2019-01-15 10:15 ` Paolo Bonzini
2019-01-23 18:25 ` Tom Roeder
2019-01-24 1:17 ` Paolo Bonzini
2019-01-15 17:51 ` Tom Roeder
2019-01-23 18:33 ` Tom Roeder [this message]
2019-01-24 1:18 ` Paolo Bonzini
2019-01-24 21:46 ` Tom Roeder
2018-11-07 12:52 ` KMSAN: kernel-infoleak in kvm_vcpu_write_guest_page Liran Alon
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