linux-kernel - Re: [PATCH net-next v3] net: Implement fault injection forcing skb reallocation

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Message-ID: <d0fa8332-aeef-4d33-9167-b9716b050594@redhat.com>
Date: Thu, 17 Oct 2024 15:50:41 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Breno Leitao <leitao@...ian.org>, Akinobu Mita <akinobu.mita@...il.com>,
 Jonathan Corbet <corbet@....net>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: kernel-team@...a.com, Pavel Begunkov <asml.silence@...il.com>,
 Mina Almasry <almasrymina@...gle.com>,
 Oleksij Rempel <o.rempel@...gutronix.de>,
 Kuniyuki Iwashima <kuniyu@...zon.com>,
 Alexander Lobakin <aleksander.lobakin@...el.com>,
 "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
 open list <linux-kernel@...r.kernel.org>,
 "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v3] net: Implement fault injection forcing skb
 reallocation

On 10/14/24 15:50, Breno Leitao wrote:
> 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>

I'm sorry to nit-pick, but checkpatch laments that the new command line 
argument lacks documentation in 
Documentation/admin-guide/kernel-parameters.txt, and I feel that could 
be actually useful.

With that, feel free to include my ack in the next revision,

Thanks!

Paolo