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

[Simon Horman]

On Wed, Mar 19, 2025 at 09:22:25AM +0800, jianqi.ren.cn@xxxxxxxxxxxxx wrote:
> From: Jakub Kicinski <kuba@xxxxxxxxxx>
> 
> [ 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@xxxxxxxxxxxxxxx>
> Fixes: e5cf1baf92cb ("act_mirred: use TC_ACT_REINSERT when possible")
> Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
> Acked-by: Jamal Hadi Salim <jhs@xxxxxxxxxxxx>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
> Signed-off-by: Jianqi Ren <jianqi.ren.cn@xxxxxxxxxxxxx>
> Signed-off-by: He Zhe <zhe.he@xxxxxxxxxxxxx>
> ---
> 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?