From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ben Greear , Johannes Berg Subject: [PATCH 4.9 014/206] mac80211: initialize fast-xmit info later Date: Tue, 10 Jan 2017 14:34:57 +0100 Message-Id: <20170110131503.396903517@linuxfoundation.org> In-Reply-To: <20170110131502.767555407@linuxfoundation.org> References: <20170110131502.767555407@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Johannes Berg commit 35f432a03e41d3bf08c51ede917f94e2288fbe8c upstream. In ieee80211_xmit_fast(), 'info' is initialized to point to the skb that's passed in, but that skb may later be replaced by a clone (if it was shared), leading to an invalid pointer. This can lead to use-after-free and also later crashes since the real SKB's info->hw_queue doesn't get initialized properly. Fix this by assigning info only later, when it's needed, after the skb replacement (may have) happened. Reported-by: Ben Greear Signed-off-by: Johannes Berg Signed-off-by: Greg Kroah-Hartman --- net/mac80211/tx.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/net/mac80211/tx.c +++ b/net/mac80211/tx.c @@ -3262,7 +3262,7 @@ static bool ieee80211_xmit_fast(struct i int extra_head = fast_tx->hdr_len - (ETH_HLEN - 2); int hw_headroom = sdata->local->hw.extra_tx_headroom; struct ethhdr eth; - struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); + struct ieee80211_tx_info *info; struct ieee80211_hdr *hdr = (void *)fast_tx->hdr; struct ieee80211_tx_data tx; ieee80211_tx_result r; @@ -3326,6 +3326,7 @@ static bool ieee80211_xmit_fast(struct i memcpy(skb->data + fast_tx->da_offs, eth.h_dest, ETH_ALEN); memcpy(skb->data + fast_tx->sa_offs, eth.h_source, ETH_ALEN); + info = IEEE80211_SKB_CB(skb); memset(info, 0, sizeof(*info)); info->band = fast_tx->band; info->control.vif = &sdata->vif;