linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
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?

  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

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=20190123183322.GB160275@google.com \
    --to=tmroeder@google.com \
    --cc=bp@alien8.de \
    --cc=hpa@zytor.com \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=liran.alon@oracle.com \
    --cc=mingo@redhat.com \
    --cc=pbonzini@redhat.com \
    --cc=rkrcmar@redhat.com \
    --cc=sean.j.christopherson@intel.com \
    --cc=syzbot+ded1696f6b50b615b630@syzkaller.appspotmail.com \
    --cc=tglx@linutronix.de \
    --cc=x86@kernel.org \
    /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).