[RFC PATCH 2/2] hw/usb/dev-uas: Report command additional adb length as unsupported

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

We are not ready to handle additional CDB data.

If a guest send a packet with such additional data,
report the command parameter as not supported.

We can then explicit there is nothing in this additional
buffer, by fixing its size to zero.

This fixes an error when building with Clang 11:

  usb/dev-uas.c:157:31: error: field 'status' with variable sized type 'uas_iu' not at the end of a struct or class is a GNU extension [-Werror,-Wgnu-variable-sized-type-not-at-end]
      uas_iu                    status;
                                ^

Reported-by: Daniele Buono <dbuono@linux.vnet.ibm.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
Cc: Ed Maste <emaste@FreeBSD.org>
Cc: Han Han <hhan@redhat.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 hw/usb/dev-uas.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/hw/usb/dev-uas.c b/hw/usb/dev-uas.c
index cec071d96c4..b6434ad4b9c 100644
--- a/hw/usb/dev-uas.c
+++ b/hw/usb/dev-uas.c
@@ -16,6 +16,7 @@
 #include "qemu/error-report.h"
 #include "qemu/main-loop.h"
 #include "qemu/module.h"
+#include "qemu/log.h"
 
 #include "hw/usb.h"
 #include "migration/vmstate.h"
@@ -70,7 +71,7 @@ typedef struct {
     uint8_t    reserved_2;
     uint64_t   lun;
     uint8_t    cdb[16];
-    uint8_t    add_cdb[];
+    uint8_t    add_cdb[0];      /* not supported by QEMU */
 } QEMU_PACKED  uas_iu_command;
 
 typedef struct {
@@ -700,6 +701,11 @@ static void usb_uas_command(UASDevice *uas, uas_iu *iu)
     uint32_t len;
     uint16_t tag = be16_to_cpu(iu->hdr.tag);
 
+    if (iu->command.add_cdb_length > 0) {
+        qemu_log_mask(LOG_UNIMP, "additional adb length not yet supported\n");
+        goto unsupported_len;
+    }
+
     if (uas_using_streams(uas) && tag > UAS_MAX_STREAMS) {
         goto invalid_tag;
     }
@@ -735,6 +741,10 @@ static void usb_uas_command(UASDevice *uas, uas_iu *iu)
     }
     return;
 
+unsupported_len:
+    usb_uas_queue_fake_sense(uas, tag, sense_code_INVALID_PARAM_VALUE);
+    return;
+
 invalid_tag:
     usb_uas_queue_fake_sense(uas, tag, sense_code_INVALID_TAG);
     return;
-- 
2.26.2