netdev - Re: [PATCH net v2] ip6mr: fix stale iterator

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Message-Id: <20180131.103400.2134338827807349026.davem@davemloft.net>
Date:   Wed, 31 Jan 2018 10:34:00 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     nikolay@...ulusnetworks.com
Cc:     netdev@...r.kernel.org, yoshfuji@...ux-ipv6.org,
        syzkaller-bugs@...glegroups.com,
        bot+eceb3204562c41a438fa1f2335e0fe4f6886d669@...kaller.appspotmail.com,
        kuznet@....inr.ac.ru, roopa@...ulusnetworks.com,
        ebiggers3@...il.com
Subject: Re: [PATCH net v2] ip6mr: fix stale iterator

From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Date: Wed, 31 Jan 2018 16:29:30 +0200

> When we dump the ip6mr mfc entries via proc, we initialize an iterator
> with the table to dump but we don't clear the cache pointer which might
> be initialized from a prior read on the same descriptor that ended. This
> can result in lock imbalance (an unnecessary unlock) leading to other
> crashes and hangs. Clear the cache pointer like ipmr does to fix the issue.
> Thanks for the reliable reproducer.
> 
> Here's syzbot's trace:
 ...
> Reported-by: syzbot <bot+eceb3204562c41a438fa1f2335e0fe4f6886d669@...kaller.appspotmail.com>
> Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
> ---
> v2: make sure the trace doesn't ruin the patch
> No fixes tag because it seems this has been there forever.

Applied and queued up for -stable.