Re: [PATCH] e1000: fix tx re-entrancy problem

[Philippe Mathieu-Daudé]

On 12/16/21 16:51, Jon Maloy wrote:
> On 12/16/21 04:36, Philippe Mathieu-Daudé wrote:
>> Hi Jon,
>>
>> On 10/21/21 18:10, Jon Maloy wrote:
>>> The fact that the MMIO handler is not re-entrant causes an infinite
>>> loop under certain conditions:
>>>
>>> Guest write to TDT ->  Loopback -> RX (DMA to TDT) -> TX
>>>
>>> We now eliminate the effect of this problem locally in e1000, by adding
>>> a boolean in struct E1000State indicating when the TX side is busy. This
>>> will cause any entering new call to return early instead of interfering
>>> with the ongoing work, and eliminates any risk of looping.
>>>
>>> This is intended to address CVE-2021-20257.
>>>
>>> Signed-off-by: Jon Maloy <jmaloy@redhat.com>
>>> ---
>>>   hw/net/e1000.c | 7 +++++++
>>>   1 file changed, 7 insertions(+)
>> I can not find the reproducer in the repository, have you sent one?
>>
> No, I did not add it to the repo.
> It was referenced from the tracker BZ, but I was unable to get access
> back then.
> It ended up with that I had it sent by mail to me directly.
> 
> What is your question? Is it that it should be in the repo, or that you
> cannot find it?

Well I'd like to reproduce the bug, but first I can not find it ;)
Having such reproducer committed along with the fix help catching
future regressions if we refactor code elsewhere.