netdev - Re: [PATCH net] netconsole: Acquire su_mutex before navigating configs hierarchy

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Message-ID: <20251031175446.24e280fa@kernel.org>
Date: Fri, 31 Oct 2025 17:54:46 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Gustavo Luiz Duarte <gustavold@...il.com>
Cc: Breno Leitao <leitao@...ian.org>, Andrew Lunn <andrew+netdev@...n.ch>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Matthew Wood
 <thepacketgeek@...il.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] netconsole: Acquire su_mutex before navigating
 configs hierarchy

On Wed, 29 Oct 2025 13:50:24 -0700 Gustavo Luiz Duarte wrote:
> There is a race between operations that iterate over the userdata
> cg_children list and concurrent add/remove of userdata items through
> configfs. The update_userdata() function iterates over the
> nt->userdata_group.cg_children list, and count_extradata_entries() also
> iterates over this same list to count nodes.

Teaching syzbot how to create a netconsole would probably go a long way
towards catching these sort of issues. Looks like right now syzbot has
coverage only for the paths that don't need a target:
https://syzkaller.appspot.com/upstream/coverage?period=month