netdev - Re: [PATCH net] dccp: defer ccid_hc_tx

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Date:   Wed, 16 Aug 2017 14:27:14 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     eric.dumazet@...il.com
Cc:     netdev@...r.kernel.org, gerrit@....abdn.ac.uk
Subject: Re: [PATCH net] dccp: defer ccid_hc_tx_delete() at dismantle time

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Wed, 16 Aug 2017 07:03:15 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> syszkaller team reported another problem in DCCP [1]
> 
> Problem here is that the structure holding RTO timer
> (ccid2_hc_tx_rto_expire() handler) is freed too soon.
> 
> We can not use del_timer_sync() to cancel the timer
> since this timer wants to grab socket lock (that would risk a dead lock)
> 
> Solution is to defer the freeing of memory when all references to
> the socket were released. Socket timers do own a reference, so this
> should fix the issue.
> 
> [1]
> ==================================================================
> BUG: KASAN: use-after-free in ccid2_hc_tx_rto_expire+0x51c/0x5c0 net/dccp/ccids/ccid2.c:144
 ...
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Dmitry Vyukov <dvyukov@...gle.com>

Applied and queued up for -stable, thanks.