From a93db944b6250d4345ed30095001f8bee5ecaed7 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Wed, 30 Jul 2014 14:55:26 +0200 Subject: [PATCH] nl80211: clear skb cb before passing to netlink commit bd8c78e78d5011d8111bc2533ee73b13a3bd6c42 upstream. In testmode and vendor command reply/event SKBs we use the skb cb data to store nl80211 parameters between allocation and sending. This causes the code for CONFIG_NETLINK_MMAP to get confused, because it takes ownership of the skb cb data when the SKB is handed off to netlink, and it doesn't explicitly clear it. Clear the skb cb explicitly when we're done and before it gets passed to netlink to avoid this issue. Reported-by: Assaf Azulay Reported-by: David Spinadel Signed-off-by: Johannes Berg [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- net/wireless/nl80211.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c index 6d4d26321028..cdf77a261509 100644 --- a/net/wireless/nl80211.c +++ b/net/wireless/nl80211.c @@ -4804,6 +4804,9 @@ int cfg80211_testmode_reply(struct sk_buff *skb) void *hdr = ((void **)skb->cb)[1]; struct nlattr *data = ((void **)skb->cb)[2]; + /* clear CB data for netlink core to own from now on */ + memset(skb->cb, 0, sizeof(skb->cb)); + if (WARN_ON(!rdev->testmode_info)) { kfree_skb(skb); return -EINVAL; @@ -4830,6 +4833,9 @@ void cfg80211_testmode_event(struct sk_buff *skb, gfp_t gfp) void *hdr = ((void **)skb->cb)[1]; struct nlattr *data = ((void **)skb->cb)[2]; + /* clear CB data for netlink core to own from now on */ + memset(skb->cb, 0, sizeof(skb->cb)); + nla_nest_end(skb, data); genlmsg_end(skb, hdr); genlmsg_multicast_netns(wiphy_net(&rdev->wiphy), skb, 0, -- 2.39.2