From 56ea977b0fc3d2e7e68e5a93a2b44aa3e25e34ed Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Mon, 16 May 2016 17:28:16 +0800 Subject: [PATCH] UPSTREAM: netlink: Fix dump skb leak/double free (cherry picked from 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 Change-Id: Ie2db6a32a49686c6d22c4a88c251b288343c7813 Bug: 33393474 --- 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 59651af8cc27..ff36e88d19d9 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: