linux-kernel - Re: [RFC PATCH 6.1.y] net/sched: act_mirred: don't override retval if we already lost the skb

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Message-ID: <20250321180101.GP892515@horms.kernel.org>
Date: Fri, 21 Mar 2025 18:01:01 +0000
From: Simon Horman <horms@...nel.org>
To: jianqi.ren.cn@...driver.com
Cc: stable@...r.kernel.org, patches@...ts.linux.dev,
	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, netdev@...r.kernel.org,
	michal.swiatkowski@...ux.intel.com
Subject: Re: [RFC PATCH 6.1.y] net/sched: act_mirred: don't override retval
 if we already lost the skb

On Wed, Mar 19, 2025 at 09:22:25AM +0800, jianqi.ren.cn@...driver.com wrote:
> From: Jakub Kicinski <kuba@...nel.org>
> 
> [ Upstream commit 166c2c8a6a4dc2e4ceba9e10cfe81c3e469e3210 ]
> 
> If we're redirecting the skb, and haven't called tcf_mirred_forward(),
> yet, we need to tell the core to drop the skb by setting the retcode
> to SHOT. If we have called tcf_mirred_forward(), however, the skb
> is out of our hands and returning SHOT will lead to UaF.
> 
> Move the retval override to the error path which actually need it.
> 
> Reviewed-by: Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>
> Fixes: e5cf1baf92cb ("act_mirred: use TC_ACT_REINSERT when possible")
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> Acked-by: Jamal Hadi Salim <jhs@...atatu.com>
> Signed-off-by: David S. Miller <davem@...emloft.net>
> Signed-off-by: Jianqi Ren <jianqi.ren.cn@...driver.com>
> Signed-off-by: He Zhe <zhe.he@...driver.com>
> ---
> Verified the build test

Sorry if it is obvious, but I'm confused by the intention of posting
an RFC for stable. Are you asking for buy-in regarding backporting
this patch to 6.1.y because for some reason it hasn't already propagated
there?