From: "Michael S. Tsirkin" <mst@redhat.com>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>, Arnd Bergmann <arnd@arndb.de>,
Amit Shah <amit@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
elena.reshetova@intel.com, kirill.shutemov@linux.intel.com
Subject: Re: [PATCH v1 2/6] virtio console: Harden port adding
Date: Fri, 27 Jan 2023 07:12:52 -0500 [thread overview]
Message-ID: <20230127071152-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <87k018p4xs.fsf@ubik.fi.intel.com>
On Fri, Jan 27, 2023 at 01:55:43PM +0200, Alexander Shishkin wrote:
> "Michael S. Tsirkin" <mst@redhat.com> writes:
>
> > On Thu, Jan 19, 2023 at 10:13:18PM +0200, Alexander Shishkin wrote:
> >> When handling control messages, instead of peeking at the device memory
> >> to obtain bits of the control structure,
> >
> > Except the message makes it seem that we are getting data from
> > device memory, when we do nothing of the kind.
>
> We can be, see below.
>
> >> take a snapshot of it once and
> >> use it instead, to prevent it from changing under us. This avoids races
> >> between port id validation and control event decoding, which can lead
> >> to, for example, a NULL dereference in port removal of a nonexistent
> >> port.
> >>
> >> The control structure is small enough (8 bytes) that it can be cached
> >> directly on the stack.
> >
> > I still have no real idea why we want a copy here.
> > If device can poke anywhere at memory then it can crash kernel anyway.
> > If there's a bounce buffer or an iommu or some other protection
> > in place, then this memory can no longer change by the time
> > we look at it.
>
> We can have shared pages between the host and guest without bounce
> buffers in between, so they can be both looking directly at the same
> page.
>
> Regards,
How does this configuration work? What else is in this page?
> --
> Alex
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WARNING: multiple messages have this Message-ID (diff)
From: "Michael S. Tsirkin" <mst@redhat.com>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
jasowang@redhat.com, virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, elena.reshetova@intel.com,
kirill.shutemov@linux.intel.com, Andi Kleen <ak@linux.intel.com>,
Amit Shah <amit@kernel.org>, Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v1 2/6] virtio console: Harden port adding
Date: Fri, 27 Jan 2023 07:12:52 -0500 [thread overview]
Message-ID: <20230127071152-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <87k018p4xs.fsf@ubik.fi.intel.com>
On Fri, Jan 27, 2023 at 01:55:43PM +0200, Alexander Shishkin wrote:
> "Michael S. Tsirkin" <mst@redhat.com> writes:
>
> > On Thu, Jan 19, 2023 at 10:13:18PM +0200, Alexander Shishkin wrote:
> >> When handling control messages, instead of peeking at the device memory
> >> to obtain bits of the control structure,
> >
> > Except the message makes it seem that we are getting data from
> > device memory, when we do nothing of the kind.
>
> We can be, see below.
>
> >> take a snapshot of it once and
> >> use it instead, to prevent it from changing under us. This avoids races
> >> between port id validation and control event decoding, which can lead
> >> to, for example, a NULL dereference in port removal of a nonexistent
> >> port.
> >>
> >> The control structure is small enough (8 bytes) that it can be cached
> >> directly on the stack.
> >
> > I still have no real idea why we want a copy here.
> > If device can poke anywhere at memory then it can crash kernel anyway.
> > If there's a bounce buffer or an iommu or some other protection
> > in place, then this memory can no longer change by the time
> > we look at it.
>
> We can have shared pages between the host and guest without bounce
> buffers in between, so they can be both looking directly at the same
> page.
>
> Regards,
How does this configuration work? What else is in this page?
> --
> Alex
next prev parent reply other threads:[~2023-01-27 12:13 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-19 13:57 [PATCH v1 0/6] Harden a few virtio bits Alexander Shishkin
2023-01-19 13:57 ` [PATCH v1 1/6] virtio console: Harden multiport against invalid host input Alexander Shishkin
2023-01-19 15:17 ` Greg Kroah-Hartman
2023-01-19 15:17 ` Greg Kroah-Hartman
2023-01-19 18:52 ` Alexander Shishkin
2023-01-19 19:18 ` Greg Kroah-Hartman
2023-01-19 19:18 ` Greg Kroah-Hartman
2023-01-19 19:34 ` Alexander Shishkin
2023-01-20 13:01 ` Michael S. Tsirkin
2023-01-20 13:01 ` Michael S. Tsirkin
2023-01-20 15:51 ` Alexander Shishkin
2023-01-19 13:57 ` [PATCH v1 2/6] virtio console: Harden port adding Alexander Shishkin
2023-01-19 15:20 ` Greg Kroah-Hartman
2023-01-19 15:20 ` Greg Kroah-Hartman
2023-01-19 17:48 ` Alexander Shishkin
2023-01-19 18:57 ` Greg Kroah-Hartman
2023-01-19 18:57 ` Greg Kroah-Hartman
2023-01-19 20:13 ` Alexander Shishkin
2023-01-20 7:15 ` Greg Kroah-Hartman
2023-01-20 7:15 ` Greg Kroah-Hartman
2023-01-27 11:02 ` Michael S. Tsirkin
2023-01-27 11:02 ` Michael S. Tsirkin
2023-01-27 11:55 ` Alexander Shishkin
2023-01-27 12:12 ` Michael S. Tsirkin [this message]
2023-01-27 12:12 ` Michael S. Tsirkin
2023-01-27 12:47 ` Alexander Shishkin
2023-01-27 13:31 ` Greg Kroah-Hartman
2023-01-27 13:31 ` Greg Kroah-Hartman
2023-01-27 14:17 ` Alexander Shishkin
2023-01-27 14:37 ` Greg Kroah-Hartman
2023-01-27 14:37 ` Greg Kroah-Hartman
2023-01-27 14:46 ` Michael S. Tsirkin
2023-01-27 14:46 ` Michael S. Tsirkin
2023-02-02 12:02 ` Reshetova, Elena
2023-01-27 13:52 ` Michael S. Tsirkin
2023-01-27 13:52 ` Michael S. Tsirkin
2023-01-20 12:59 ` Michael S. Tsirkin
2023-01-20 12:59 ` Michael S. Tsirkin
2023-01-19 13:57 ` [PATCH v1 3/6] virtio 9p: Fix an overflow Alexander Shishkin
2023-01-20 12:54 ` Michael S. Tsirkin
2023-01-20 12:54 ` Michael S. Tsirkin
2023-01-20 16:29 ` Alexander Shishkin
2023-01-19 13:57 ` [PATCH v1 4/6] virtio console: Harden control message handling Alexander Shishkin
2023-01-19 15:22 ` Greg Kroah-Hartman
2023-01-19 15:22 ` Greg Kroah-Hartman
2023-01-20 12:45 ` Michael S. Tsirkin
2023-01-20 12:45 ` Michael S. Tsirkin
2023-01-20 16:41 ` Alexander Shishkin
2023-01-27 10:58 ` Michael S. Tsirkin
2023-01-27 10:58 ` Michael S. Tsirkin
2023-01-27 12:04 ` Alexander Shishkin
2023-01-19 13:57 ` [PATCH v1 5/6] virtio_net: Guard against buffer length overflow in xdp_linearize_page() Alexander Shishkin
2023-01-20 13:09 ` Michael S. Tsirkin
2023-01-20 13:09 ` Michael S. Tsirkin
2023-01-19 13:57 ` [PATCH v1 6/6] virtio_ring: Prevent bounds check bypass on descriptor index Alexander Shishkin
2023-01-20 12:56 ` Michael S. Tsirkin
2023-01-20 12:56 ` Michael S. Tsirkin
2023-01-20 11:55 ` [PATCH v1 0/6] Harden a few virtio bits Michael S. Tsirkin
2023-01-20 11:55 ` Michael S. Tsirkin
2023-01-20 12:32 ` Alexander Shishkin
2023-01-20 12:40 ` Michael S. Tsirkin
2023-01-20 12:40 ` Michael S. Tsirkin
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