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Violators will be prosecuted; Mon, 26 Sep 2016 02:34:19 -0600 Received: from b03cxnp08025.gho.boulder.ibm.com (b03cxnp08025.gho.boulder.ibm.com [9.17.130.17]) by d03dlp03.boulder.ibm.com (Postfix) with ESMTP id 58AB219D801C; Mon, 26 Sep 2016 02:33:47 -0600 (MDT) Received: from b03ledav006.gho.boulder.ibm.com (b03ledav006.gho.boulder.ibm.com [9.17.130.237]) by b03cxnp08025.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u8Q8YIkK3211712; Mon, 26 Sep 2016 01:34:18 -0700 Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 438C2C6047; Mon, 26 Sep 2016 02:34:18 -0600 (MDT) Received: from [192.168.66.108] (unknown [9.84.96.44]) by b03ledav006.gho.boulder.ibm.com (Postfix) with ESMTP id C7939C603E; Mon, 26 Sep 2016 02:34:15 -0600 (MDT) From: Greg Kurz To: qemu-devel@nongnu.org Date: Mon, 26 Sep 2016 10:34:15 +0200 In-Reply-To: <147487882735.6679.8076815106195077844.stgit@bahia> References: <147487882735.6679.8076815106195077844.stgit@bahia> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16092608-8235-0000-0000-000009467A1E X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00005813; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000185; SDB=6.00761409; UDB=6.00362632; IPR=6.00536326; BA=6.00004756; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00012783; XFM=3.00000011; UTC=2016-09-26 08:34:22 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16092608-8236-0000-0000-0000352576BB Message-Id: <147487885500.6679.17365810852820160326.stgit@bahia> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2016-09-26_05:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=3 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1609020000 definitions=main-1609260162 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] X-Received-From: 148.163.156.1 Subject: [Qemu-devel] [PATCH v3 3/9] virtio-9p: handle handle_9p_output() error X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , "Michael S. Tsirkin" , Jason Wang , Greg Kurz , Max Reitz , "Aneesh Kumar K.V" , Stefan Hajnoczi , Cornelia Huck , Paolo Bonzini Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" A broken guest may send a request without providing buffers for the reply or for the request itself, and virtqueue_pop() will return an element with either in_num == 0 or out_num == 0. All 9P requests are expected to start with the following 7-byte header: uint32_t size_le; uint8_t id; uint16_t tag_le; If iov_to_buf() fails to return these 7 bytes, then something is wrong in the guest. In both cases, it is wrong to crash QEMU, since the root cause lies in the guest. This patch hence does the following: - keep the check of in_num since pdu_complete() assumes it has enough space to store the reply and we will send something broken to the guest - let iov_to_buf() handle out_num == 0, since it will return 0 just like if the guest had provided an zero-sized buffer. - call virtio_error() to inform the guest that the device is now broken, instead of aborting - detach the request from the virtqueue and free it Signed-off-by: Greg Kurz Reviewed-by: Stefan Hajnoczi --- v3: - dropped the out_num check (already covered by iov_to_buf()) - reworded the in_num error message - added an error path to detach and free the virtqueue element I haven't added the R-b tags received during v2 because of the above changes. --- hw/9pfs/virtio-9p-device.c | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-) diff --git a/hw/9pfs/virtio-9p-device.c b/hw/9pfs/virtio-9p-device.c index e7ea0e45f3dd..a338f6400264 100644 --- a/hw/9pfs/virtio-9p-device.c +++ b/hw/9pfs/virtio-9p-device.c @@ -41,6 +41,7 @@ static void handle_9p_output(VirtIODevice *vdev, VirtQueue *vq) V9fsState *s = &v->state; V9fsPDU *pdu; ssize_t len; + VirtQueueElement *elem; while ((pdu = pdu_alloc(s))) { struct { @@ -48,21 +49,28 @@ static void handle_9p_output(VirtIODevice *vdev, VirtQueue *vq) uint8_t id; uint16_t tag_le; } QEMU_PACKED out; - VirtQueueElement *elem; elem = virtqueue_pop(vq, sizeof(VirtQueueElement)); if (!elem) { - pdu_free(pdu); - break; + goto out_free_pdu; } - BUG_ON(elem->out_num == 0 || elem->in_num == 0); + if (elem->in_num == 0) { + virtio_error(vdev, + "The guest sent a VirtFS request without space for " + "the reply"); + goto out_free_req; + } QEMU_BUILD_BUG_ON(sizeof(out) != 7); v->elems[pdu->idx] = elem; len = iov_to_buf(elem->out_sg, elem->out_num, 0, &out, sizeof(out)); - BUG_ON(len != sizeof(out)); + if (len != sizeof(out)) { + virtio_error(vdev, "The guest sent a malformed VirtFS request: " + "header size is %zd, should be 7", len); + goto out_free_req; + } pdu->size = le32_to_cpu(out.size_le); @@ -72,6 +80,14 @@ static void handle_9p_output(VirtIODevice *vdev, VirtQueue *vq) qemu_co_queue_init(&pdu->complete); pdu_submit(pdu); } + + return; + +out_free_req: + virtqueue_detach_element(vq, elem, 0); + g_free(elem); +out_free_pdu: + pdu_free(pdu); } static uint64_t virtio_9p_get_features(VirtIODevice *vdev, uint64_t features,