netdev - Re: [PATCH net] net/packet: move reference count in packet

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Message-ID: <be8c4d7a-e27c-7bde-280a-ff2444657b7b@iogearbox.net>
Date: Fri, 1 Dec 2023 10:19:35 +0100
From: Daniel Borkmann <daniel@...earbox.net>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, netdev@...r.kernel.org
Cc: "The UK's National Cyber Security Centre (NCSC)" <security@...c.gov.uk>,
 stable <stable@...nel.org>
Subject: Re: [PATCH net] net/packet: move reference count in packet_sock to 64
 bits

On 11/30/23 4:15 PM, Willem de Bruijn wrote:
> Daniel Borkmann wrote:
>> On 11/30/23 3:20 PM, Greg Kroah-Hartman wrote:
>>> In some potential instances the reference count on struct packet_sock
>>> could be saturated and cause overflows which gets the kernel a bit
>>> confused.  To prevent this, move to a 64bit atomic reference count to
>>> prevent the possibility of this type of overflow.
>>>
>>> Because we can not handle saturation, using refcount_t is not possible
>>> in this place.  Maybe someday in the future if it changes could it be
>>> used.
>>>
>>> Original version from Daniel after I did it wrong, I've provided a
>>> changelog.
>>>
>>> Reported-by: "The UK's National Cyber Security Centre (NCSC)" <security@...c.gov.uk>
>>> Cc: stable <stable@...nel.org>
>>> Cc: Daniel Borkmann <daniel@...earbox.net>
>>> Cc: Willem de Bruijn <willemdebruijn.kernel@...il.com>
>>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>>
>> Thanks!
>>
>> Acked-by: Daniel Borkmann <daniel@...earbox.net>
> 
> Acked-by: Willem de Bruijn <willemb@...gle.com>

There was feedback from Linus that switching to atomic_long_t is better
choice so that it doesn't penalize 32-bit architectures. Will post a v2
today.

Thanks,
Daniel