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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.

Fixes: 16b304f340 ("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>
This commit is contained in:
Herbert Xu 2016-05-16 17:28:16 +08:00 committed by David S. Miller
parent 45e093ae28
commit 92964c79b3
1 changed files with 5 additions and 2 deletions
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7
net/netlink/af_netlink.c
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@ -2059,6 +2059,7 @@ 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_min_size;
int alloc_size;
@ -2134,9 +2135,11 @@ 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: