linux-kernel - Re: net: GPF in __netlink_ns

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Date:	Wed, 20 Jan 2016 23:00:20 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	"Wan, Kaike" <kaike.wan@...el.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Richard Weinberger <richard.weinberger@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Thomas Graf <tgraf@...g.ch>,
	Daniel Borkmann <daniel@...earbox.net>,
	Ken-ichirou MATSUZAWA <chamaken@...il.com>,
	Nicolas Dichtel <nicolas.dichtel@...nd.com>,
	Florian Westphal <fw@...len.de>,
	netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	syzkaller <syzkaller@...glegroups.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	"Fleck, John" <john.fleck@...el.com>,
	"Weiny, Ira" <ira.weiny@...el.com>,
	Doug Ledford <dledford@...hat.com>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Subject: Re: net: GPF in __netlink_ns_capable

On Wed, Jan 20, 2016 at 02:35:59PM +0000, Wan, Kaike wrote:
> >From the code (netlink_dump() in net/netlink/af_netlink.c), it shows that a skb is allocated without initializing the skb->cb[] field, which will cause oops if netlink_capable() is called with the duplicate skb. This will happen if the netlink_dump_start() path is followed (in ibnl_rcv_msg() in drivers/infiniband/core/netlink.c). However, for the IB netlink local service, we handle only request RDMA_NL_LS_OP_SET_TIMEOUT and response to RDMA_NL_LS_OP_RESOLVE, which directly call the registered dump function (ib_nl_handle_resolve_resp() and ib_nl_handle_resolve_resp()). See the following snippet:

You'll find a reproducer in the original email:

http://lkml.iu.edu/hypermail/linux/kernel/1601.1/06505.html

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt