inet: frag: don't re-use chainlist for evictor
authorFlorian Westphal <fw@strlen.de>
Thu, 23 Jul 2015 10:05:37 +0000 (12:05 +0200)
committerDavid S. Miller <davem@davemloft.net>
Mon, 27 Jul 2015 04:00:14 +0000 (21:00 -0700)
commitd1fe19444d82e399e38c1594c71b850eca8e9de0
treed71cf0c7d0e7bd2ab28c68bb189e73826cbb0681
parent81296fc67319d96ea6f7f43a07494394e1236a19
inet: frag: don't re-use chainlist for evictor

commit 65ba1f1ec0eff ("inet: frags: fix a race between inet_evict_bucket
and inet_frag_kill") describes the bug, but the fix doesn't work reliably.

Problem is that ->flags member can be set on other cpu without chainlock
being held by that task, i.e. the RMW-Cycle can clear INET_FRAG_EVICTED
bit after we put the element on the evictor private list.

We can crash when walking the 'private' evictor list since an element can
be deleted from list underneath the evictor.

Join work with Nikolay Alexandrov.

Fixes: b13d3cbfb8e8 ("inet: frag: move eviction of queues to work queue")
Reported-by: Johan Schuijt <johan@transip.nl>
Tested-by: Frank Schreuder <fschreuder@transip.nl>
Signed-off-by: Nikolay Alexandrov <nikolay@cumulusnetworks.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
include/net/inet_frag.h
net/ipv4/inet_fragment.c