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

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Message-ID: <20241007-flat-steel-cuscus-9bffda@leitao>
Date: Mon, 7 Oct 2024 09:20:14 -0700
From: Breno Leitao <leitao@...ian.org>
To: 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>,
	Pavel Begunkov <asml.silence@...il.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 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`.

Let me spend some time and have this done.

Thanks for the feedback.
--breno