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

[Philippe Mathieu-Daudé]

On 11/30/20 10:20 AM, Mauro Matteo Cascella wrote:
> Hello,
> 
> On Mon, Nov 30, 2020 at 3:36 AM Jason Wang <jasowang@redhat.com> wrote:
>>
>>
>> On 2020/11/27 下午11:45, Philippe Mathieu-Daudé wrote:
>>> Do not allow qemu_send_packet*() and qemu_net_queue_send()
>>> functions to accept packets bigger then NET_BUFSIZE.
>>>
>>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>>> ---
>>> 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 we do want to accept bigger packets (i.e. multiple GSO packets
>>> in a IOV), we could use INT32_MAX as limit...
>>
>>
>> This looks like a complaint for:
>>
>> commit 25c01bd19d0e4b66f357618aeefda1ef7a41e21a
>> Author: Jason Wang <jasowang@redhat.com>
>> Date:   Tue Dec 4 11:53:43 2018 +0800
>>
>>      net: drop too large packet early
>>
>> which only fixes the iov version of the function.
>>
>> If you don't see any real bug, I suggest to merge the fix in next release.

Fine by me, I don't have access to the big picture.

> Following is the reference bug along with a proposed patch, although I
> guess the patch [2] is not strictly required once this patchset is
> merged.
> 
> [1] https://bugzilla.redhat.com/show_bug.cgi?id=1899722
> [2] https://lists.nongnu.org/archive/html/qemu-devel/2020-11/msg05935.html

I didn't noticed your patch. While it prevents this kind of
error on a particular device, it doesn't for the rest.