net: drop too large packet early
We try to detect and drop too large packet (>INT_MAX) in 1592a9947036
("net: ignore packet size greater than INT_MAX") during packet
delivering. Unfortunately, this is not sufficient as we may hit
another integer overflow when trying to queue such large packet in
qemu_net_queue_append_iov():
- size of the allocation may overflow on 32bit
- packet->size is integer which may overflow even on 64bit
Fixing this by moving the check to qemu_sendv_packet_async() which is
the entrance of all networking codes and reduce the limit to
NET_BUFSIZE to be more conservative. This works since:
- For the callers that call qemu_sendv_packet_async() directly, they
only care about if zero is returned to determine whether to prevent
the source from producing more packets. A callback will be triggered
if peer can accept more then source could be enabled. This is
usually used by high speed networking implementation like virtio-net
or netmap.
- For the callers that call qemu_sendv_packet() that calls
qemu_sendv_packet_async() indirectly, they often ignore the return
value. In this case qemu will just the drop packets if peer can't
receive.
Qemu will copy the packet if it was queued. So it was safe for both
kinds of the callers to assume the packet was sent.
Since we move the check from qemu_deliver_packet_iov() to
qemu_sendv_packet_async(), it would be safer to make
qemu_deliver_packet_iov() static to prevent any external user in the
future.
This is a revised patch of CVE-2018-17963.
Cc: qemu-stable@nongnu.org
Cc: Li Qiang <liq3ea@163.com>
Fixes: 1592a9947036 ("net: ignore packet size greater than INT_MAX")
Reported-by: Li Qiang <liq3ea@gmail.com>
Reviewed-by: Li Qiang <liq3ea@gmail.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-id: 20181204035347.6148-2-jasowang@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2 files changed
