linux-kernel - Re: [PATCH net-next v6 1/8] net: add get_netmem/put

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Message-ID: <20250228163846.0a59fb40@kernel.org>
Date: Fri, 28 Feb 2025 16:38:46 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Mina Almasry <almasrymina@...gle.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
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 <jhs@...atatu.com>, Victor Nogueira <victor@...atatu.com>, Pedro Tammela
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Subject: Re: [PATCH net-next v6 1/8] net: add get_netmem/put_netmem support

On Thu, 27 Feb 2025 04:12:02 +0000 Mina Almasry wrote:
>  static inline void __skb_frag_ref(skb_frag_t *frag)
>  {
> -	get_page(skb_frag_page(frag));
> +	get_netmem(skb_frag_netmem(frag));
>  }

Silently handling types of memory the caller may not be expecting
always worries me. Why do we need this? 

In general, I'm surprised by the lack of bug reports for devmem.
Can you think of any way we could expose this more to syzbot?
First thing that comes to mind is a simple hack in netdevsim,
to make it insert a netmem handle (allocated locally, not a real
memory provider), every N packets (controllable via debugfs).
Would that work?