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Commit 57b26930 authored by Herbert Xu's avatar Herbert Xu Committed by Sasha Levin
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netlink: Fix dump skb leak/double free 



[ Upstream commit 92964c79b357efd980812c4de5c1fd2ec8bb5520 ]

When we free cb->skb after a dump, we do it after releasing the
lock.  This means that a new dump could have started in the time
being and we'll end up freeing their skb instead of ours.

This patch saves the skb and module before we unlock so we free
the right memory.

Fixes: 16b304f3 ("netlink: Eliminate kmalloc in netlink dump operation.")
Reported-by: default avatarBaozeng Ding <sploving1@gmail.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Acked-by: default avatarCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarSasha Levin <sasha.levin@oracle.com>
parent 624a4c64

net/netlink/af_netlink.c

+5 −2
Original line number Diff line number Diff line
@@ -2630,6 +2630,7 @@ static int netlink_dump(struct sock *sk) 
	struct netlink_callback *cb;

	struct sk_buff *skb = NULL;

	struct nlmsghdr *nlh;

	struct module *module;

	int len, err = -ENOBUFS;

	int alloc_size;
@@ -2699,9 +2700,11 @@ static int netlink_dump(struct sock *sk) 
		cb->done(cb);



	nlk->cb_running = false;

	module = cb->module;

	skb = cb->skb;

	mutex_unlock(nlk->cb_mutex);

	module_put(cb->module);

	consume_skb(cb->skb);

	module_put(module);

	consume_skb(skb);

	return 0;



errout_skb: