netdev - Re: [PATCH v2 1/1] net/sched: cls_u32: Fix reference counter leak leading to overflow

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Date: Thu, 8 Jun 2023 09:31:07 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Lee Jones <lee@...nel.org>
Cc: jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us, 
	davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, 
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org, stable@...nel.org
Subject: Re: [PATCH v2 1/1] net/sched: cls_u32: Fix reference counter leak
 leading to overflow

On Thu, Jun 8, 2023 at 9:29 AM Lee Jones <lee@...nel.org> wrote:
>
> In the event of a failure in tcf_change_indev(), u32_set_parms() will
> immediately return without decrementing the recently incremented
> reference counter.  If this happens enough times, the counter will
> rollover and the reference freed, leading to a double free which can be
> used to do 'bad things'.
>
> In order to prevent this, move the point of possible failure above the
> point where the reference counter is incremented.  Also save any
> meaningful return values to be applied to the return data at the
> appropriate point in time.
>
> This issue was caught with KASAN.
>
> Fixes: 705c7091262d ("net: sched: cls_u32: no need to call tcf_exts_change for newly allocated struct")
> Suggested-by: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Lee Jones <lee@...nel.org>
> ---

Thanks Lee !

Reviewed-by: Eric Dumazet <edumazet@...gle.com>