linux-kernel - Re: [PATCH net-next] net: Implement fault injection forcing skb reallocation

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Message-ID: <9386a9fc-a8b5-41fc-9f92-f621e56a918d@gmail.com>
Date: Mon, 7 Oct 2024 17:48:39 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: Breno Leitao <leitao@...ian.org>, Akinobu Mita <akinobu.mita@...il.com>
Cc: kuba@...nel.org, davem@...emloft.net, edumazet@...gle.com,
 pabeni@...hat.com, Jonathan Corbet <corbet@....net>, horms@...nel.org,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 Mina Almasry <almasrymina@...gle.com>, Willem de Bruijn
 <willemb@...gle.com>, Alexander Lobakin <aleksander.lobakin@...el.com>,
 "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH net-next] net: Implement fault injection forcing skb
 reallocation

On 10/7/24 17:20, Breno Leitao wrote:
> On Sat, Oct 05, 2024 at 01:38:59PM +0900, Akinobu Mita wrote:
>> 2024年10月2日(水) 20:37 Breno Leitao <leitao@...ian.org>:
>>>
>>> Introduce a fault injection mechanism to force skb reallocation. The
>>> primary goal is to catch bugs related to pointer invalidation after
>>> potential skb reallocation.
>>>
>>> The fault injection mechanism aims to identify scenarios where callers
>>> retain pointers to various headers in the skb but fail to reload these
>>> pointers after calling a function that may reallocate the data. This
>>> type of bug can lead to memory corruption or crashes if the old,
>>> now-invalid pointers are used.
>>>
>>> By forcing reallocation through fault injection, we can stress-test code
>>> paths and ensure proper pointer management after potential skb
>>> reallocations.
>>>
>>> Add a hook for fault injection in the following functions:
>>>
>>>   * pskb_trim_rcsum()
>>>   * pskb_may_pull_reason()
>>>   * pskb_trim()
>>>
>>> As the other fault injection mechanism, protect it under a debug Kconfig
>>> called CONFIG_FAIL_SKB_FORCE_REALLOC.
>>>
>>> This patch was *heavily* inspired by Jakub's proposal from:
>>> https://lore.kernel.org/all/20240719174140.47a868e6@kernel.org/
>>>
>>> CC: Akinobu Mita <akinobu.mita@...il.com>
>>> Suggested-by: Jakub Kicinski <kuba@...nel.org>
>>> Signed-off-by: Breno Leitao <leitao@...ian.org>
>>
>> This new addition seems sensible.  It might be more useful to have a filter
>> that allows you to specify things like protocol family.
> 
> I think it might make more sense to be network interface specific. For
> instance, only fault inject in interface `ethx`.

Wasn't there some error injection infra that allows to optionally
run bpf? That would cover the filtering problem. ALLOW_ERROR_INJECTION,
maybe?

-- 
Pavel Begunkov