wifi: mac80211: check skb_shared in ieee80211_8023_xmit()

Add a missing skb_shared check into 802.3 path to prevent potential
use-after-free from happening. This also uses skb_share_check()
instead of open-coding in tx path.

Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Link: https://lore.kernel.org/r/e7a73aaf7742b17e43421c56625646dfc5c4d2cb.1653571902.git.ryder.lee@mediatek.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 0e4efc0..c425f4f 100644 (file)
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -2818,19 +2818,10 @@ static struct sk_buff *ieee80211_build_hdr(struct ieee80211_sub_if_data *sdata,
        /*
         * If the skb is shared we need to obtain our own copy.
         */
-       if (skb_shared(skb)) {
-               struct sk_buff *tmp_skb = skb;
-
-               /* can't happen -- skb is a clone if info_id != 0 */
-               WARN_ON(info_id);
-
-               skb = skb_clone(skb, GFP_ATOMIC);
-               kfree_skb(tmp_skb);
-
-               if (!skb) {
-                       ret = -ENOMEM;
-                       goto free;
-               }
+       skb = skb_share_check(skb, GFP_ATOMIC);
+       if (unlikely(!skb)) {
+               ret = -ENOMEM;
+               goto free;
        }
 
        hdr.frame_control = fc;
@@ -3539,15 +3530,9 @@ static bool ieee80211_xmit_fast(struct ieee80211_sub_if_data *sdata,
 
        /* after this point (skb is modified) we cannot return false */
 
-       if (skb_shared(skb)) {
-               struct sk_buff *tmp_skb = skb;
-
-               skb = skb_clone(skb, GFP_ATOMIC);
-               kfree_skb(tmp_skb);
-
-               if (!skb)
-                       return true;
-       }
+       skb = skb_share_check(skb, GFP_ATOMIC);
+       if (unlikely(!skb))
+               return true;
 
        if ((hdr->frame_control & cpu_to_le16(IEEE80211_STYPE_QOS_DATA)) &&
            ieee80211_amsdu_aggregate(sdata, sta, fast_tx, skb))
@@ -4437,7 +4422,7 @@ static void ieee80211_8023_xmit(struct ieee80211_sub_if_data *sdata,
                                struct net_device *dev, struct sta_info *sta,
                                struct ieee80211_key *key, struct sk_buff *skb)
 {
-       struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+       struct ieee80211_tx_info *info;
        struct ieee80211_local *local = sdata->local;
        struct tid_ampdu_tx *tid_tx;
        u8 tid;
@@ -4452,6 +4437,11 @@ static void ieee80211_8023_xmit(struct ieee80211_sub_if_data *sdata,
            test_bit(SDATA_STATE_OFFCHANNEL, &sdata->state))
                goto out_free;
 
+       skb = skb_share_check(skb, GFP_ATOMIC);
+       if (unlikely(!skb))
+               return;
+
+       info = IEEE80211_SKB_CB(skb);
        memset(info, 0, sizeof(*info));
 
        ieee80211_aggr_check(sdata, sta, skb);