4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Johannes Berg <johannes.b...@intel.com>
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 <gree...@candelatech.com>
Signed-off-by: Johannes Berg <johannes.b...@intel.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
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;
