From: Eric Dumazet <eric.dumazet@gmail.com>
To: David Miller <davem@davemloft.net>
Cc: yanmin_zhang@linux.intel.com, kunx.jiang@intel.com,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ipv4: fix the rcu race between free_fib_info and ip_route_output_slow
Date: Wed, 23 May 2012 06:37:09 +0200 [thread overview]
Message-ID: <1337747829.3361.1599.camel@edumazet-glaptop> (raw)
In-Reply-To: <20120522.232310.911242148705021745.davem@davemloft.net>
On Tue, 2012-05-22 at 23:23 -0400, David Miller wrote:
> From: Yanmin Zhang <yanmin_zhang@linux.intel.com>
> Date: Wed, 23 May 2012 11:02:03 +0800
>
> > 1) Why does free_fib_info call call_rcu instead of releasing fi directly?
> > I assume other cpu might be accessing it. nexthop_nh->nh_dev is in fi.
> > If other cpu are accessing it, here resetting to NULL would cause other
> > cpu panic.
>
> Because fib trie lookups are done with RCU locking, therefore we must
> use RCU freeing to release the object.
>
> What I was trying to impart to you is that removing the NULL
> assignment is wrong and that an alternative fix is warranted (hint:
> consider moving something into the RCU release).
> --
Its more than that I'm afraid.
fi->fib_dev (aka fib_nh[0].nh_dev) need full RCU protection.
Also the "fib_info_cnt--;" must stay in free_fib_info() (so that it is
protected by RTNL)
next prev parent reply other threads:[~2012-05-23 4:37 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-22 9:48 [PATCH] ipv4: fix the rcu race between free_fib_info and ip_route_output_slow kun.jiang
2012-05-22 19:15 ` David Miller
2012-05-23 3:02 ` Yanmin Zhang
2012-05-23 3:23 ` David Miller
2012-05-23 3:30 ` Yanmin Zhang
2012-05-23 3:49 ` David Miller
2012-05-23 4:41 ` Yanmin Zhang
2012-05-23 5:08 ` Eric Dumazet
2012-05-23 4:37 ` Eric Dumazet [this message]
2012-05-23 4:54 ` Yanmin Zhang
2012-05-23 5:02 ` Eric Dumazet
2012-05-23 6:15 ` Yanmin Zhang
2012-05-23 6:27 ` Eric Dumazet
2012-05-23 6:47 ` Yanmin Zhang
2012-05-23 6:55 ` Eric Dumazet
2012-05-23 7:13 ` Eric Dumazet
2012-05-23 7:24 ` Yanmin Zhang
2012-05-23 7:39 ` Eric Dumazet
2012-05-23 7:41 ` Eric Dumazet
2012-05-23 7:47 ` Yanmin Zhang
2012-05-23 6:37 ` Eric Dumazet
2012-05-23 6:43 ` Eric Dumazet
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