netdev - Re: [PATCH] xen-netfront: handle NULL returned by xdp_convert_buff_to

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <ed8dec2a-f507-49be-a6f3-fb8a91bfef01@suse.com>
Date: Thu, 17 Apr 2025 10:51:17 +0200
From: Juergen Gross <jgross@...e.com>
To: Alexey <sdl@...ct.ru>, Jakub Kicinski <kuba@...nel.org>
Cc: Stefano Stabellini <sstabellini@...nel.org>,
 Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 Jesper Dangaard Brouer <hawk@...nel.org>,
 John Fastabend <john.fastabend@...il.com>, xen-devel@...ts.xenproject.org,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
 lvc-project@...uxtesting.org, stable@...r.kernel.org
Subject: Re: [PATCH] xen-netfront: handle NULL returned by
 xdp_convert_buff_to_frame()

On 17.04.25 10:45, Alexey wrote:
> 
> On 17.04.2025 10:12, Jürgen Groß wrote:
>> On 17.04.25 09:00, Alexey wrote:
>>>
>>> On 17.04.2025 03:58, Jakub Kicinski wrote:
>>>> On Mon, 14 Apr 2025 18:34:01 +0000 Alexey Nepomnyashih wrote:
>>>>>           get_page(pdata);
>>>> Please notice this get_page() here.
>>>>
>>>>>           xdpf = xdp_convert_buff_to_frame(xdp);
>>>>> +        if (unlikely(!xdpf)) {
>>>>> +            trace_xdp_exception(queue->info->netdev, prog, act);
>>>>> +            break;
>>>>> +        }
>>> Do you mean that it would be better to move the get_page(pdata) call lower,
>>> after checking for NULL in xdpf, so that the reference count is only increased
>>> after a successful conversion?
>>
>> I think the error handling here is generally broken (or at least very
>> questionable).
>>
>> I suspect that in case of at least some errors the get_page() is leaking
>> even without this new patch.
>>
>> In case I'm wrong a comment reasoning why there is no leak should be
>> added.
>>
>>
>> Juergen
> 
> I think pdata is freed in xdp_return_frame_rx_napi() -> __xdp_return()

Agreed. But what if xennet_xdp_xmit() returns an error < 0?

In this case xdp_return_frame_rx_napi() won't be called.

Juergen

Download attachment "OpenPGP_0xB0DE9DD628BF132F.asc" of type "application/pgp-keys" (3684 bytes)

Download attachment "OpenPGP_signature.asc" of type "application/pgp-signature" (496 bytes)