Re: [RFC PATCH-for-5.2 1/2] net: Do not accept packets bigger then NET_BUFSIZE

[P J P]

+-- On Fri, 27 Nov 2020, Philippe Mathieu-Daudé wrote --+
| Do not allow qemu_send_packet*() and qemu_net_queue_send()
| functions to accept packets bigger then NET_BUFSIZE.
| 
| We have to put a limit somewhere. NET_BUFSIZE is defined as:
|  /* Maximum GSO packet size (64k) plus plenty of room for
|   * the ethernet and virtio_net headers
|   */
|  #define NET_BUFSIZE (4096 + 65536)
| 
| +    if (size > NET_BUFSIZE) {
| +        return -1;
| +    }
| +

/usr/include/linux/if_ether.h
  #define ETH_MIN_MTU 68        /* Min IPv4 MTU per RFC791  */                  
    
  #define ETH_MAX_MTU 0xFFFFU   /* 65535, same as IP_MAX_MTU    */

  if (size < ETH_MIN_MTU || size > ETH_MAX_MTU) {
      return -1;
  }

Should there be similar check for minimum packet size?

Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
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