netdev - Re: [PATCH net] neigh: fix use-after-free read in pneigh_get

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Message-Id: <20190616.141701.29050678945758813.davem@davemloft.net>
Date:   Sun, 16 Jun 2019 14:17:01 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        syzkaller@...glegroups.com
Subject: Re: [PATCH net] neigh: fix use-after-free read in pneigh_get_next

From: Eric Dumazet <edumazet@...gle.com>
Date: Sat, 15 Jun 2019 16:28:48 -0700

> Nine years ago, I added RCU handling to neighbours, not pneighbours.
> (pneigh are not commonly used)
> 
> Unfortunately I missed that /proc dump operations would use a
> common entry and exit point : neigh_seq_start() and neigh_seq_stop()
> 
> We need to read_lock(tbl->lock) or risk use-after-free while
> iterating the pneigh structures.
> 
> We might later convert pneigh to RCU and revert this patch.
> 
> sysbot reported :
 ...
> Fixes: 767e97e1e0db ("neigh: RCU conversion of struct neighbour")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>

Applied and queued up for -stable.