netdev - Re: [PATCH] net/802/garp: fix potential deadlock on &app->lock

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date: Tue, 27 Jun 2023 15:55:11 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Chengfeng Ye <dg573847474@...il.com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net/802/garp: fix potential deadlock on &app->lock

On Tue, Jun 27, 2023 at 12:52 PM Chengfeng Ye <dg573847474@...il.com> wrote:
>
> As &app->lock is also acquired by the timer garp_join_timer() which
> which executes under soft-irq context, code executing under process
> context should disable irq before acquiring the lock, otherwise
> deadlock could happen if the process context hold the lock then
> preempt by the interruption.
>
> garp_pdu_rcv() is one such function that acquires &app->lock, but I
> am not sure whether it is called with irq disable outside thus the
> patch could be false.
>
> Possible deadlock scenario:
> garp_pdu_rcv()
>     -> spin_lock(&app->lock)
>         <timer interrupt>

This can not happen.

RX handlers are called from BH context, and rcu_read_lock()

See net/core/dev.c,  deliver_skb() and netif_receive_skb()


>         -> garp_join_timer()
>         -> spin_lock(&app->lock)
>
> This flaw was found using an experimental static analysis tool we are
> developing for irq-related deadlock.
>
> The tentative patch fix the potential deadlock by spin_lock_irqsave(),
> or it should be fixed with spin_lock_bh() if it is a real bug? I am
> not very sure.

I guess more work is needed at your side :)