netlink: Fix dump skb leak/double free
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. Change-Id: I81f1eb1ef4951917b5db084bd7a4289222eab597 Fixes: 16b304f3404f ("netlink: Eliminate kmalloc in netlink dump operation.") Reported-by: Baozeng Ding <sploving1@gmail.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Acked-by: Cong Wang <xiyou.wangcong@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> CVE-2016-9806 Signed-off-by: Kevin F. Haggerty <haggertk@lineageos.org>
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@ -1695,6 +1695,7 @@ static int netlink_dump(struct sock *sk)
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struct netlink_callback *cb;
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struct sk_buff *skb = NULL;
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struct nlmsghdr *nlh;
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struct module *module;
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int len, err = -ENOBUFS;
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int alloc_size;
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@ -1740,9 +1741,10 @@ static int netlink_dump(struct sock *sk)
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if (cb->done)
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cb->done(cb);
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nlk->cb = NULL;
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module = cb->module;
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mutex_unlock(nlk->cb_mutex);
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module_put(cb->module);
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module_put(module);
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netlink_destroy_callback(cb);
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return 0;
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