netdev - Re: [PATCH net-next] net/sched: unregister lockdep keys in qdisc_create/qdisc

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Message-ID: <ZjIY3hkW8dYRPzSI@shredder>
Date: Wed, 1 May 2024 13:26:38 +0300
From: Ido Schimmel <idosch@...sch.org>
To: Davide Caratti <dcaratti@...hat.com>
Cc: Jamal Hadi Salim <jhs@...atatu.com>,
	Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Naresh Kamboju <naresh.kamboju@...aro.org>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net/sched: unregister lockdep keys in
 qdisc_create/qdisc_alloc error path

On Tue, Apr 30, 2024 at 07:11:13PM +0200, Davide Caratti wrote:
> Naresh and Eric report several errors (corrupted elements in the dynamic
> key hash list), when running tdc.py or syzbot. The error path of
> qdisc_alloc() and qdisc_create() frees the qdisc memory, but it forgets
> to unregister the lockdep key, thus causing use-after-free like the
> following one:

[...]

> Fix this ensuring that lockdep_unregister_key() is called before the
> qdisc struct is freed, also in the error path of qdisc_create() and
> qdisc_alloc().
> 
> Fixes: af0cb3fa3f9e ("net/sched: fix false lockdep warning on qdisc root lock")
> Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>
> Closes: https://lore.kernel.org/netdev/20240429221706.1492418-1-naresh.kamboju@linaro.org/
> CC: Naresh Kamboju <naresh.kamboju@...aro.org>
> CC: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Davide Caratti <dcaratti@...hat.com>

Reviewed-by: Ido Schimmel <idosch@...dia.com>

We've also hit the issue on two of our machines running debug kernels. I
started a run with the fix on both and will report tomorrow morning (not
saying you should wait).