netdev - Re: [PATCH v3] net: sched: crash on blocks with goto chain action

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Message-Id: <20171205.112213.619683454960802411.davem@davemloft.net>
Date:   Tue, 05 Dec 2017 11:22:13 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     code@...pl.cz
Cc:     netdev@...r.kernel.org, xiyou.wangcong@...il.com, jiri@...nulli.us
Subject: Re: [PATCH v3] net: sched: crash on blocks with goto chain action

From: Roman Kapl <code@...pl.cz>
Date: Wed, 29 Nov 2017 20:20:14 +0100

> tcf_block_put_ext has assumed that all filters (and thus their goto
> actions) are destroyed in RCU callback and so can not race with our
> list iteration. However, that is not true during netns cleanup (see
> tcf_exts_get_net comment). The assumption was broken by the patch series
> c7e460ce5572..623859ae06b8 ("Merge branch 'net-sched-race-fix'").
> 
> Prevent the user after free by holding all chains (except 0, that one is
> already held) as it was done before
> 822e86d997e4 ("net_sched: remove tcf_block_put_deferred()").
> 
> To reproduce, run the following in a netns and then delete the ns:
>     ip link add dtest type dummy
>     tc qdisc add dev dtest ingress
>     tc filter add dev dtest chain 1 parent ffff: handle 1 prio 1 flower action goto chain 2
> 
> Fixes: 623859ae06b8 ("Merge branch 'net-sched-race-fix'")
> Signed-off-by: Roman Kapl <code@...pl.cz>

This doesn't apply cleanly to 'net'.