scsi: Add buf_len parameter to scsi_req_new()

When a SCSI command is received from the guest, the CDB length implied
by the first byte might exceed the number of bytes the guest sent. In
this case scsi_req_new() will read uninitialized data, causing
unpredictable behavior.

Adds the buf_len parameter to scsi_req_new() and plumbs it through the
call stack.

Signed-off-by: John Millikin <john@john-millikin.com>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1127
Message-Id: <20220817053458.698416-1-john@john-millikin.com>
[Fill in correct length for adapters other than ESP. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/scsi/esp.c

@@ -292,7 +292,7 @@ static void do_command_phase(ESPState *s)
     esp_fifo_pop_buf(&s->cmdfifo, buf, cmdlen);
 
     current_lun = scsi_device_find(&s->bus, 0, s->current_dev->id, s->lun);
-    s->current_req = scsi_req_new(current_lun, 0, s->lun, buf, s);
+    s->current_req = scsi_req_new(current_lun, 0, s->lun, buf, cmdlen, s);
     datalen = scsi_req_enqueue(s->current_req);
     s->ti_size = datalen;
     fifo8_reset(&s->cmdfifo);

hw/scsi/lsi53c895a.c

@@ -864,7 +864,7 @@ static void lsi_do_command(LSIState *s)
     s->current = g_new0(lsi_request, 1);
     s->current->tag = s->select_tag;
     s->current->req = scsi_req_new(dev, s->current->tag, s->current_lun, buf,
-                                   s->current);
+                                   s->dbc, s->current);
 
     n = scsi_req_enqueue(s->current->req);
     if (n) {

hw/scsi/megasas.c

@@ -1062,7 +1062,7 @@ static int megasas_pd_get_info_submit(SCSIDevice *sdev, int lun,
         info->inquiry_data[0] = 0x7f; /* Force PQual 0x3, PType 0x1f */
         info->vpd_page83[0] = 0x7f;
         megasas_setup_inquiry(cmdbuf, 0, sizeof(info->inquiry_data));
-        cmd->req = scsi_req_new(sdev, cmd->index, lun, cmdbuf, cmd);
+        cmd->req = scsi_req_new(sdev, cmd->index, lun, cmdbuf, sizeof(cmdbuf), cmd);
         if (!cmd->req) {
             trace_megasas_dcmd_req_alloc_failed(cmd->index,
                                                 "PD get info std inquiry");
@@ -1080,7 +1080,7 @@ static int megasas_pd_get_info_submit(SCSIDevice *sdev, int lun,
         return MFI_STAT_INVALID_STATUS;
     } else if (info->inquiry_data[0] != 0x7f && info->vpd_page83[0] == 0x7f) {
         megasas_setup_inquiry(cmdbuf, 0x83, sizeof(info->vpd_page83));
-        cmd->req = scsi_req_new(sdev, cmd->index, lun, cmdbuf, cmd);
+        cmd->req = scsi_req_new(sdev, cmd->index, lun, cmdbuf, sizeof(cmdbuf), cmd);
         if (!cmd->req) {
             trace_megasas_dcmd_req_alloc_failed(cmd->index,
                                                 "PD get info vpd inquiry");
@@ -1268,7 +1268,7 @@ static int megasas_ld_get_info_submit(SCSIDevice *sdev, int lun,
         cmd->iov_buf = g_malloc0(dcmd_size);
         info = cmd->iov_buf;
         megasas_setup_inquiry(cdb, 0x83, sizeof(info->vpd_page83));
-        cmd->req = scsi_req_new(sdev, cmd->index, lun, cdb, cmd);
+        cmd->req = scsi_req_new(sdev, cmd->index, lun, cdb, sizeof(cdb), cmd);
         if (!cmd->req) {
             trace_megasas_dcmd_req_alloc_failed(cmd->index,
                                                 "LD get info vpd inquiry");
@@ -1748,7 +1748,7 @@ static int megasas_handle_scsi(MegasasState *s, MegasasCmd *cmd,
         return MFI_STAT_SCSI_DONE_WITH_ERROR;
     }
 
-    cmd->req = scsi_req_new(sdev, cmd->index, lun_id, cdb, cmd);
+    cmd->req = scsi_req_new(sdev, cmd->index, lun_id, cdb, cdb_len, cmd);
     if (!cmd->req) {
         trace_megasas_scsi_req_alloc_failed(
                 mfi_frame_desc(frame_cmd), target_id, lun_id);
@@ -1823,7 +1823,7 @@ static int megasas_handle_io(MegasasState *s, MegasasCmd *cmd, int frame_cmd)
 
     megasas_encode_lba(cdb, lba_start, lba_count, is_write);
     cmd->req = scsi_req_new(sdev, cmd->index,
-                            lun_id, cdb, cmd);
+                            lun_id, cdb, cdb_len, cmd);
     if (!cmd->req) {
         trace_megasas_scsi_req_alloc_failed(
             mfi_frame_desc(frame_cmd), target_id, lun_id);

hw/scsi/mptsas.c

@@ -324,7 +324,8 @@ static int mptsas_process_scsi_io_request(MPTSASState *s,
     }
 
     req->sreq = scsi_req_new(sdev, scsi_io->MsgContext,
-                            scsi_io->LUN[1], scsi_io->CDB, req);
+                             scsi_io->LUN[1], scsi_io->CDB,
+                             scsi_io->CDBLength, req);
 
     if (req->sreq->cmd.xfer > scsi_io->DataLength) {
         goto overrun;

hw/scsi/scsi-bus.c

@@ -102,15 +102,15 @@ static void scsi_device_unrealize(SCSIDevice *s)
 }
 
 int scsi_bus_parse_cdb(SCSIDevice *dev, SCSICommand *cmd, uint8_t *buf,
-                       void *hba_private)
+                       size_t buf_len, void *hba_private)
 {
     SCSIBus *bus = DO_UPCAST(SCSIBus, qbus, dev->qdev.parent_bus);
     int rc;
 
     assert(cmd->len == 0);
-    rc = scsi_req_parse_cdb(dev, cmd, buf);
+    rc = scsi_req_parse_cdb(dev, cmd, buf, buf_len);
     if (bus->info->parse_cdb) {
-        rc = bus->info->parse_cdb(dev, cmd, buf, hba_private);
+        rc = bus->info->parse_cdb(dev, cmd, buf, buf_len, hba_private);
     }
     return rc;
 }
@@ -703,7 +703,7 @@ SCSIRequest *scsi_req_alloc(const SCSIReqOps *reqops, SCSIDevice *d,
 }
 
 SCSIRequest *scsi_req_new(SCSIDevice *d, uint32_t tag, uint32_t lun,
-                          uint8_t *buf, void *hba_private)
+                          uint8_t *buf, size_t buf_len, void *hba_private)
 {
     SCSIBus *bus = DO_UPCAST(SCSIBus, qbus, d->qdev.parent_bus);
     const SCSIReqOps *ops;
@@ -734,9 +734,9 @@ SCSIRequest *scsi_req_new(SCSIDevice *d, uint32_t tag, uint32_t lun,
     }
 
     if (ops != NULL || !sc->parse_cdb) {
-        ret = scsi_req_parse_cdb(d, &cmd, buf);
+        ret = scsi_req_parse_cdb(d, &cmd, buf, buf_len);
     } else {
-        ret = sc->parse_cdb(d, &cmd, buf, hba_private);
+        ret = sc->parse_cdb(d, &cmd, buf, buf_len, hba_private);
     }
 
     if (ret != 0) {
@@ -1308,7 +1308,8 @@ static void scsi_cmd_xfer_mode(SCSICommand *cmd)
     }
 }
 
-int scsi_req_parse_cdb(SCSIDevice *dev, SCSICommand *cmd, uint8_t *buf)
+int scsi_req_parse_cdb(SCSIDevice *dev, SCSICommand *cmd, uint8_t *buf,
+                       size_t buf_len)
 {
     int rc;
     int len;
@@ -1713,7 +1714,11 @@ static int get_scsi_requests(QEMUFile *f, void *pv, size_t size,
         qemu_get_buffer(f, buf, sizeof(buf));
         qemu_get_be32s(f, &tag);
         qemu_get_be32s(f, &lun);
-        req = scsi_req_new(s, tag, lun, buf, NULL);
+        /*
+         * A too-short CDB would have been rejected by scsi_req_new, so just use
+         * SCSI_CMD_BUF_SIZE as the CDB length.
+         */
+        req = scsi_req_new(s, tag, lun, buf, sizeof(buf), NULL);
         req->retry = (sbyte == 1);
         if (bus->info->load_request) {
             req->hba_private = bus->info->load_request(f, req);

hw/scsi/scsi-disk.c

@@ -3030,14 +3030,15 @@ static SCSIRequest *scsi_block_new_request(SCSIDevice *d, uint32_t tag,
 }
 
 static int scsi_block_parse_cdb(SCSIDevice *d, SCSICommand *cmd,
-                                  uint8_t *buf, void *hba_private)
+                                  uint8_t *buf, size_t buf_len,
+                                  void *hba_private)
 {
     SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, d);
 
     if (scsi_block_is_passthrough(s, buf)) {
-        return scsi_bus_parse_cdb(&s->qdev, cmd, buf, hba_private);
+        return scsi_bus_parse_cdb(&s->qdev, cmd, buf, buf_len, hba_private);
     } else {
-        return scsi_req_parse_cdb(&s->qdev, cmd, buf);
+        return scsi_req_parse_cdb(&s->qdev, cmd, buf, buf_len);
     }
 }
 

hw/scsi/scsi-generic.c

@@ -791,9 +791,10 @@ static Property scsi_generic_properties[] = {
 };
 
 static int scsi_generic_parse_cdb(SCSIDevice *dev, SCSICommand *cmd,
-                                  uint8_t *buf, void *hba_private)
+                                  uint8_t *buf, size_t buf_len,
+                                  void *hba_private)
 {
-    return scsi_bus_parse_cdb(dev, cmd, buf, hba_private);
+    return scsi_bus_parse_cdb(dev, cmd, buf, buf_len, hba_private);
 }
 
 static void scsi_generic_class_initfn(ObjectClass *klass, void *data)

hw/scsi/spapr_vscsi.c

@@ -783,6 +783,7 @@ static int vscsi_queue_cmd(VSCSIState *s, vscsi_req *req)
     union srp_iu *srp = &req_iu(req)->srp;
     SCSIDevice *sdev;
     int n, lun;
+    size_t cdb_len = sizeof (srp->cmd.cdb) + (srp->cmd.add_cdb_len & ~3);
 
     if ((srp->cmd.lun == 0 || be64_to_cpu(srp->cmd.lun) == SRP_REPORT_LUNS_WLUN)
       && srp->cmd.cdb[0] == REPORT_LUNS) {
@@ -801,7 +802,7 @@ static int vscsi_queue_cmd(VSCSIState *s, vscsi_req *req)
         } return 1;
     }
 
-    req->sreq = scsi_req_new(sdev, req->qtag, lun, srp->cmd.cdb, req);
+    req->sreq = scsi_req_new(sdev, req->qtag, lun, srp->cmd.cdb, cdb_len, req);
     n = scsi_req_enqueue(req->sreq);
 
     trace_spapr_vscsi_queue_cmd(req->qtag, srp->cmd.cdb[0],

hw/scsi/virtio-scsi.c

@@ -622,7 +622,8 @@ static void virtio_scsi_command_complete(SCSIRequest *r, size_t resid)
 }
 
 static int virtio_scsi_parse_cdb(SCSIDevice *dev, SCSICommand *cmd,
-                                 uint8_t *buf, void *hba_private)
+                                 uint8_t *buf, size_t buf_len,
+                                 void *hba_private)
 {
     VirtIOSCSIReq *req = hba_private;
 
@@ -696,7 +697,7 @@ static int virtio_scsi_handle_cmd_req_prepare(VirtIOSCSI *s, VirtIOSCSIReq *req)
     virtio_scsi_ctx_check(s, d);
     req->sreq = scsi_req_new(d, req->req.cmd.tag,
                              virtio_scsi_get_lun(req->req.cmd.lun),
-                             req->req.cmd.cdb, req);
+                             req->req.cmd.cdb, vs->cdb_size, req);
 
     if (req->sreq->cmd.mode != SCSI_XFER_NONE
         && (req->sreq->cmd.mode != req->mode ||

hw/scsi/vmw_pvscsi.c

@@ -730,7 +730,7 @@ pvscsi_process_request_descriptor(PVSCSIState *s,
         r->sg.elemAddr = descr->dataAddr;
     }
 
-    r->sreq = scsi_req_new(d, descr->context, r->lun, descr->cdb, r);
+    r->sreq = scsi_req_new(d, descr->context, r->lun, descr->cdb, descr->cdbLen, r);
     if (r->sreq->cmd.mode == SCSI_XFER_FROM_DEV &&
         (descr->flags & PVSCSI_FLAG_CMD_DIR_TODEVICE)) {
         r->cmp.hostStatus = BTSTAT_BADMSG;

hw/usb/dev-storage.c

@@ -415,7 +415,7 @@ static void usb_msd_handle_data(USBDevice *dev, USBPacket *p)
                                      cbw.cmd_len, s->data_len);
             assert(le32_to_cpu(s->csw.residue) == 0);
             s->scsi_len = 0;
-            s->req = scsi_req_new(scsi_dev, tag, cbw.lun, cbw.cmd, NULL);
+            s->req = scsi_req_new(scsi_dev, tag, cbw.lun, cbw.cmd, cbw.cmd_len, NULL);
             if (s->commandlog) {
                 scsi_req_print(s->req);
             }

hw/usb/dev-uas.c

@@ -71,7 +71,7 @@ typedef struct {
     uint8_t    reserved_2;
     uint64_t   lun;
     uint8_t    cdb[16];
-    uint8_t    add_cdb[1];      /* not supported by QEMU */
+    uint8_t    add_cdb[1];
 } QEMU_PACKED  uas_iu_command;
 
 typedef struct {
@@ -699,6 +699,7 @@ static void usb_uas_command(UASDevice *uas, uas_iu *iu)
     UASRequest *req;
     uint32_t len;
     uint16_t tag = be16_to_cpu(iu->hdr.tag);
+    size_t cdb_len = sizeof(iu->command.cdb) + iu->command.add_cdb_length;
 
     if (iu->command.add_cdb_length > 0) {
         qemu_log_mask(LOG_UNIMP, "additional adb length not yet supported\n");
@@ -729,7 +730,7 @@ static void usb_uas_command(UASDevice *uas, uas_iu *iu)
 
     req->req = scsi_req_new(req->dev, req->tag,
                             usb_uas_get_lun(req->lun),
-                            iu->command.cdb, req);
+                            iu->command.cdb, cdb_len, req);
     if (uas->requestlog) {
         scsi_req_print(req->req);
     }

include/hw/scsi/scsi.h

@@ -59,7 +59,7 @@ struct SCSIDeviceClass {
     void (*realize)(SCSIDevice *dev, Error **errp);
     void (*unrealize)(SCSIDevice *dev);
     int (*parse_cdb)(SCSIDevice *dev, SCSICommand *cmd, uint8_t *buf,
-                     void *hba_private);
+                     size_t buf_len, void *hba_private);
     SCSIRequest *(*alloc_req)(SCSIDevice *s, uint32_t tag, uint32_t lun,
                               uint8_t *buf, void *hba_private);
     void (*unit_attention_reported)(SCSIDevice *s);
@@ -122,7 +122,7 @@ struct SCSIBusInfo {
     int tcq;
     int max_channel, max_target, max_lun;
     int (*parse_cdb)(SCSIDevice *dev, SCSICommand *cmd, uint8_t *buf,
-                     void *hba_private);
+                     size_t buf_len, void *hba_private);
     void (*transfer_data)(SCSIRequest *req, uint32_t arg);
     void (*fail)(SCSIRequest *req);
     void (*complete)(SCSIRequest *req, size_t residual);
@@ -192,14 +192,15 @@ void scsi_legacy_handle_cmdline(void);
 SCSIRequest *scsi_req_alloc(const SCSIReqOps *reqops, SCSIDevice *d,
                             uint32_t tag, uint32_t lun, void *hba_private);
 SCSIRequest *scsi_req_new(SCSIDevice *d, uint32_t tag, uint32_t lun,
-                          uint8_t *buf, void *hba_private);
+                          uint8_t *buf, size_t buf_len, void *hba_private);
 int32_t scsi_req_enqueue(SCSIRequest *req);
 SCSIRequest *scsi_req_ref(SCSIRequest *req);
 void scsi_req_unref(SCSIRequest *req);
 
 int scsi_bus_parse_cdb(SCSIDevice *dev, SCSICommand *cmd, uint8_t *buf,
-                       void *hba_private);
-int scsi_req_parse_cdb(SCSIDevice *dev, SCSICommand *cmd, uint8_t *buf);
+                       size_t buf_len, void *hba_private);
+int scsi_req_parse_cdb(SCSIDevice *dev, SCSICommand *cmd, uint8_t *buf,
+                       size_t buf_len);
 void scsi_req_build_sense(SCSIRequest *req, SCSISense sense);
 void scsi_req_print(SCSIRequest *req);
 void scsi_req_continue(SCSIRequest *req);