From aa0731ad108cc8f4a928b5fa1862fba0c17a9a62 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. Fixes: abb6cd1d1e1d ("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 --- net/netlink/af_netlink.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index aeefe127691a8..627f898c05b96 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -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: -- 2.39.5