[Qemu-devel] [PATCH 3/3] usb-ccid: add check message size checks

[Gerd Hoffmann]

Check message size too when figuring whenever we should expect more data.
Fix debug message to show useful data, p->iov.size is fixed anyway if we
land there, print how much we got meanwhile instead.

Also check announced message size against actual message size.  That
is a more general fix for CVE-2017-5898 than commit "c7dfbf3 usb: ccid:
check ccid apdu length".

Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
---
 hw/usb/dev-smartcard-reader.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/hw/usb/dev-smartcard-reader.c b/hw/usb/dev-smartcard-reader.c
index 1acc1fb..7cd4ed0 100644
--- a/hw/usb/dev-smartcard-reader.c
+++ b/hw/usb/dev-smartcard-reader.c
@@ -1011,12 +1011,19 @@ static void ccid_handle_bulk_out(USBCCIDState *s, 
USBPacket *p)
     }
 
     ccid_header = (CCID_Header *)s->bulk_out_data;
-    if (p->iov.size == CCID_MAX_PACKET_SIZE) {
+    if ((s->bulk_out_pos - 10 < ccid_header->dwLength) &&
+        (p->iov.size == CCID_MAX_PACKET_SIZE)) {
         DPRINTF(s, D_VERBOSE,
-            "usb-ccid: bulk_in: expecting more packets (%zd/%d)\n",
-            p->iov.size, ccid_header->dwLength);
+                "usb-ccid: bulk_in: expecting more packets (%d/%d)\n",
+                s->bulk_out_pos - 10, ccid_header->dwLength);
         return;
     }
+    if (s->bulk_out_pos - 10 != ccid_header->dwLength) {
+        DPRINTF(s, 1,
+                "usb-ccid: bulk_in: message size mismatch (got %d, expected 
%d)\n",
+                s->bulk_out_pos - 10, ccid_header->dwLength);
+        goto err;
+    }
 
     DPRINTF(s, D_MORE_INFO, "%s %x %s\n", __func__,
             ccid_header->bMessageType,
-- 
1.8.3.1