From aef5ceb9b197eaaf92ce97373861a8014e53e64e Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Mon, 16 May 2016 17:28:16 +0800 Subject: [PATCH] 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 Signed-off-by: Herbert Xu Acked-by: Cong Wang Signed-off-by: David S. Miller CVE-2016-9806 Signed-off-by: Kevin F. Haggerty --- net/netlink/af_netlink.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index fc40cb31b3c..50437d06bfb 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -1695,6 +1695,7 @@ 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; @@ -1740,9 +1741,10 @@ static int netlink_dump(struct sock *sk) if (cb->done) cb->done(cb); nlk->cb = NULL; + module = cb->module; mutex_unlock(nlk->cb_mutex); - module_put(cb->module); + module_put(module); netlink_destroy_callback(cb); return 0;