From: Al Viro <viro@ZenIV.linux.org.uk>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: syzbot <syzbot+87cfa083e727a224754b@syzkaller.appspotmail.com>,
avagin@openvz.org, davem@davemloft.net, dingtianhong@huawei.com,
edumazet@google.com, elena.reshetova@intel.com,
jasowang@redhat.com, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, matthew@mjdsystems.ca,
mingo@kernel.org, netdev@vger.kernel.org, pabeni@redhat.com,
syzkaller-bugs@googlegroups.com,
virtualization@lists.linux-foundation.org, willemb@google.com
Subject: Re: KMSAN: uninit-value in _copy_to_iter (2)
Date: Thu, 7 Jun 2018 19:04:49 +0100 [thread overview]
Message-ID: <20180607180449.GS30522@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20180607205611-mutt-send-email-mst@kernel.org>
On Thu, Jun 07, 2018 at 08:59:06PM +0300, Michael S. Tsirkin wrote:
> On Thu, Jun 07, 2018 at 06:43:55PM +0100, Al Viro wrote:
> > On Thu, Jun 07, 2018 at 06:38:48PM +0300, Michael S. Tsirkin wrote:
> > > #syz test: https://github.com/google/kmsan.git/master d2d741e5d1898dfde1a75ea3d29a9a3e2edf0617
> > >
> > > Subject: vhost: fix info leak
> > >
> > > Fixes: CVE-2018-1118
> > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > > ---
> > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> > > index f0be5f35ab28..9beefa6ed1ce 100644
> > > --- a/drivers/vhost/vhost.c
> > > +++ b/drivers/vhost/vhost.c
> > > @@ -2345,6 +2345,9 @@ struct vhost_msg_node *vhost_new_msg(struct vhost_virtqueue *vq, int type)
> > > struct vhost_msg_node *node = kmalloc(sizeof *node, GFP_KERNEL);
> > > if (!node)
> > > return NULL;
> > > +
> > > + /* Make sure all padding within the structure is initialized. */
> > > + memset(&node->msg, 0, sizeof node->msg);
> >
> > Umm... Maybe kzalloc(), then? You have
> >
> > struct vhost_msg_node {
> > struct vhost_msg msg;
> > struct vhost_virtqueue *vq;
> > struct list_head node;
> > };
> >
> > and that's what, 68 bytes in msg, then either 4 bytes pointer or
> > 4 bytes padding + 8 bytes pointer, then two pointers? How much
> > does explicit partial memset() save you here?
>
> Yes but 0 isn't a nop here so if this struct is used without
> a sensible initialization, it will crash elsewhere.
> I prefer KASAN to catch such uses.
>
>
> > > node->vq = vq;
> > > node->msg.type = type;
IDGI - what would your variant catch that kzalloc + 2 assignments won't?
Accesses to uninitialized ->node? Because that's the only difference in
what is and is not initialized between those variants...
next prev parent reply other threads:[~2018-06-07 18:04 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-23 16:56 KMSAN: uninit-value in _copy_to_iter (2) syzbot
2018-04-25 19:19 ` syzbot
2018-06-07 15:38 ` Michael S. Tsirkin
2018-06-07 15:38 ` syzbot
2018-06-07 16:25 ` Dmitry Vyukov via Virtualization
2018-06-07 17:04 ` syzbot
2018-06-07 17:43 ` Al Viro
2018-06-07 17:59 ` Michael S. Tsirkin
2018-06-07 18:04 ` Al Viro [this message]
2018-06-07 19:29 ` Michael S. Tsirkin
2018-06-07 17:10 ` Michael S. Tsirkin
2018-06-07 17:31 ` syzbot
2018-04-27 15:45 ` [PATCH net] vhost: Use kzalloc() to allocate vhost_msg_node Kevin Easton
2018-04-27 16:05 ` Michael S. Tsirkin
2018-04-27 16:11 ` Dmitry Vyukov via Virtualization
2018-04-27 16:15 ` Michael S. Tsirkin
2018-04-27 16:25 ` Dmitry Vyukov
2018-04-27 16:29 ` Dmitry Vyukov
2018-04-27 19:36 ` Michael S. Tsirkin
2018-04-29 8:10 ` Dmitry Vyukov
2018-04-28 1:07 ` Kevin Easton
2018-04-28 1:51 ` Kevin Easton
2018-04-28 2:23 ` Jason Wang
2018-05-07 13:03 ` Michael S. Tsirkin
2018-05-07 13:12 ` Dmitry Vyukov
2018-05-08 8:27 ` Kevin Easton
2018-05-29 22:19 ` [net] " Guenter Roeck
2018-05-30 3:01 ` Michael S. Tsirkin
2018-05-30 3:42 ` Guenter Roeck
2018-06-04 12:34 ` Dmitry Vyukov via Virtualization
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=20180607180449.GS30522@ZenIV.linux.org.uk \
--to=viro@zeniv.linux.org.uk \
--cc=avagin@openvz.org \
--cc=davem@davemloft.net \
--cc=dingtianhong@huawei.com \
--cc=edumazet@google.com \
--cc=elena.reshetova@intel.com \
--cc=jasowang@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=matthew@mjdsystems.ca \
--cc=mingo@kernel.org \
--cc=mst@redhat.com \
--cc=netdev@vger.kernel.org \
--cc=pabeni@redhat.com \
--cc=syzbot+87cfa083e727a224754b@syzkaller.appspotmail.com \
--cc=syzkaller-bugs@googlegroups.com \
--cc=virtualization@lists.linux-foundation.org \
--cc=willemb@google.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).