From: Herbert Xu Date: Mon, 16 May 2016 09:28:16 +0000 (+0800) Subject: netlink: Fix dump skb leak/double free X-Git-Tag: firefly_0821_release~176^2~4^2~40^2~78 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=49543942beb1b9ca95709d6cfa67708932aa4d11;p=firefly-linux-kernel-4.4.55.git 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: 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 Signed-off-by: Greg Kroah-Hartman --- diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 992b35fb8615..7a5fa0c98377 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -2784,6 +2784,7 @@ 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; @@ -2863,9 +2864,11 @@ 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: