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Tsirkin" , Jason Wang , Mike Christie Cc: Paolo Bonzini , Stefan Hajnoczi , =?UTF-8?q?Eugenio=20P=C3=A9rez?= , Nicholas Bellinger , Asias He , virtualization@lists.linux.dev, kvm@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] vhost-scsi: fix event queue iov out-of-bounds Date: Fri, 4 Sep 2026 08:52:40 +0800 Message-Id: <20260904005240.502787-1-physicalmtea@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- 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