netdev - [RFC] ipv6: rt6_update_expires() seems racy

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Message-ID: <1361231718.19353.117.camel@edumazet-glaptop>
Date:	Mon, 18 Feb 2013 15:55:18 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>, Gao feng <gaofeng@...fujitsu.com>,
	Neil Horman <nhorman@...driver.com>,
	Jiri Bohac <jbohac@...e.cz>
Subject: [RFC] ipv6: rt6_update_expires() seems racy

Some strange crashes happen in rt6_check_expired(), with access
to random addresses.

At first glance, it looks like the RTF_EXPIRES and
stuff added in commit 1716a96101c49186b
(ipv6: fix problem with expired dst cache)
are racy : same dst could be manipulated at the same time
on different cpus.

At some point, our stack believes rt->dst.from contains a dst pointer,
while its really a jiffie value (as rt->dst.expires shares the same area
of memory)

rt6_update_expires() should be fixed, or am I missing something ?

CC Neil because of https://bugzilla.redhat.com/show_bug.cgi?id=892060

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