From: Johannes Berg <[email protected]> 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. Cc: [email protected] Reported-by: Ben Greear <[email protected]> Signed-off-by: Johannes Berg <[email protected]> --- net/mac80211/tx.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c index 4dea18be385c..3182e0c4e157 100644 --- a/net/mac80211/tx.c +++ b/net/mac80211/tx.c @@ -3288,7 +3288,7 @@ static bool ieee80211_xmit_fast(struct ieee80211_sub_if_data *sdata, 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; @@ -3352,6 +3352,7 @@ static bool ieee80211_xmit_fast(struct ieee80211_sub_if_data *sdata, 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; -- 2.9.3
