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From: "Michael S. Tsirkin" <mst@redhat.com>
To: Linus Torvalds <torvalds@linuxfoundation.org>
Cc: "David Laight" <david.laight.linux@gmail.com>,
	"Haoran Wang" <haoranwangsec@gmail.com>,
	jasowangio@gmail.com, "KVM list" <kvm@vger.kernel.org>,
	virtualization@lists.linux.dev, Netdev <netdev@vger.kernel.org>,
	"Eugenio Pérez" <eperezma@redhat.com>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"Security Officers" <security@kernel.org>
Subject: Re: [BUG] vhost/vringh: __get_user without access_ok leaks kernel memory via vDPA passthrough
Date: Sun, 18 Oct 2026 18:13:26 -0400	[thread overview]
Message-ID: <20261018181202-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <CAHk-=wjneFJ7XmZ6ux-LsHq4apDgANcKfERztmAG9sGVY_TxAg@mail.gmail.com>

On Sun, Oct 18, 2026 at 12:06:36PM -1000, Linus Torvalds wrote:
> >     > > +
> >     > > +           if (!access_ok(uaddr, sizeof(*p)))
> >     > > +                   return -EFAULT;
> >     > > +           ret = __get_user(tmp, uaddr);
> >     >
> >     > Can't that be a normal get_user() call?
> >     >
> >     > David
> 
> 
> >     Ugh, actually no. This is called under local_bh_disable.
> > 
> >     get_user would splat on might_sleep.


> I[ sorry for html - driving around ]
> 
> That's a separate bug, and you really shouldn't use __get_user to work around
> it just because it doesn't check. 
> 
> You should use pagefault_disable() around the access. And if there is still a
> sleep_on() complaint, that should be fixed. 
> 
>         Linus


Thanks Linus, will look into this.

-- 
MST


  parent reply	other threads:[~2026-10-18 22:13 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-10-15  7:23 Haoran Wang
2026-10-15  7:42 ` Eugenio Perez Martin
2026-10-17 21:59 ` David Laight
2026-10-18 19:24 ` Michael S. Tsirkin
2026-10-18 19:48   ` David Laight
2026-10-18 21:42     ` Michael S. Tsirkin
2026-10-18 21:57     ` Michael S. Tsirkin
     [not found]       ` <CAHk-=wjneFJ7XmZ6ux-LsHq4apDgANcKfERztmAG9sGVY_TxAg@mail.gmail.com>
2026-10-18 22:13         ` Michael S. Tsirkin [this message]
2026-10-18 23:12         ` Linus Torvalds
2026-10-18 20:34   ` Linus Torvalds
2026-10-18 21:11     ` Linus Torvalds
2026-10-18 21:41       ` Michael S. Tsirkin
2026-10-18 21:43     ` Michael S. Tsirkin

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