netdev - Re: [PATCH net-next v2 0/5] net/sched: improve class lifetime handling

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Date: Mon, 31 Jul 2023 09:31:42 +0200
From: Simon Horman <horms@...nel.org>
To: Pedro Tammela <pctammela@...atatu.com>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, jhs@...atatu.com,
	xiyou.wangcong@...il.com, jiri@...nulli.us
Subject: Re: [PATCH net-next v2 0/5] net/sched: improve class lifetime
 handling

On Fri, Jul 28, 2023 at 12:35:32PM -0300, Pedro Tammela wrote:
> Valis says[0]:
> ============
> Three classifiers (cls_fw, cls_u32 and cls_route) always copy
> tcf_result struct into the new instance of the filter on update.
> 
> This causes a problem when updating a filter bound to a class,
> as tcf_unbind_filter() is always called on the old instance in the
> success path, decreasing filter_cnt of the still referenced class
> and allowing it to be deleted, leading to a use-after-free.
> ============
> 
> Turns out these could have been spotted easily with proper warnings.
> Improve the current class lifetime with wrappers that check for
> overflow/underflow.
> 
> While at it add an extack for when a class in use is deleted.
> 
> [0] https://lore.kernel.org/all/20230721174856.3045-1-sec@valis.email/
> 
> v1 -> v2:
>    - Add ack tag from Jamal
>    - Move definitions to sch_generic.h as suggested by Cong

Reviewed-by: Simon Horman <horms@...nel.org>