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Tsirkin" To: Jia Jia Cc: Jason Wang , Mike Christie , Paolo Bonzini , Stefan Hajnoczi , Eugenio =?iso-8859-1?Q?P=E9rez?= , Nicholas Bellinger , Asias He , virtualization@lists.linux.dev, kvm@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] vhost-scsi: fix event queue iov out-of-bounds Message-ID: <20261102091441-mutt-send-email-mst@kernel.org> References: <20260904005240.502787-1-physicalmtea@gmail.com> X-Mailing-List: kvm@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260904005240.502787-1-physicalmtea@gmail.com> On Fri, Sep 04, 2026 at 08:52:40AM +0800, Jia Jia wrote: > vhost_scsi_do_evt_work() uses vq->iov[out] after vhost_get_vq_desc() > without checking that the descriptor chain contains an input segment. > vq->iov has UIO_MAXIOV entries (1024). A chain of 1024 output-only > descriptors yields out == 1024 and in == 0, so the length check reads > one past the end of the array. > > With a host-side harness that sets VHOST_SCSI_SET_EVENTS_MISSED and > kicks an event queue filled with 1024 OUT descriptors, UBSAN reports: > > UBSAN: array-index-out-of-bounds in drivers/vhost/scsi.c:611:14 > index 1024 is out of range for type 'iovec [1024]' > > Call Trace: > > dump_stack_lvl+0x5f/0x90 > dump_stack+0x10/0x18 > ubsan_epilogue+0x9/0x39 > __ubsan_handle_out_of_bounds.cold+0x50/0x55 > vhost_scsi_complete_events+0x55f/0x5a0 [vhost_scsi] > vhost_scsi_evt_work+0x17/0x30 [vhost_scsi] > vhost_run_work_list+0x8e/0xd0 [vhost] > vhost_task_fn+0xe1/0x210 > ret_from_fork+0x348/0x540 > ret_from_fork_asm+0x1a/0x30 > > > Require at least one input descriptor before indexing iov[out], and > treat a pure-output chain as a missed event like other invalid event > buffers. > > Fixes: a6c9af87363c ("tcm_vhost: Add hotplug/hotunplug support") > Signed-off-by: Jia Jia Applied an alternative more comprehensive patch, credited you. > --- > drivers/vhost/scsi.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c > index 9a1253b9d8c5..9b5f07f52b0c 100644 > --- a/drivers/vhost/scsi.c > +++ b/drivers/vhost/scsi.c > @@ -608,9 +608,10 @@ > return; > } > > - if ((vq->iov[out].iov_len != sizeof(struct virtio_scsi_event))) { > + if (!in || > + vq->iov[out].iov_len != sizeof(struct virtio_scsi_event)) { > vq_err(vq, "Expecting virtio_scsi_event, got %zu bytes\n", > - vq->iov[out].iov_len); > + in ? vq->iov[out].iov_len : 0); > vs->vs_events_missed = true; > return; > } > -- > 2.43.0