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   1 From: Felix Fietkau <nbd@nbd.name>
   2 Date: Mon, 28 Jan 2019 13:16:45 +0100
   3 Subject: [PATCH] mac80211: ensure that management tx skbs have encryption
   4  tailroom
   5
   6 Some drivers use IEEE80211_KEY_FLAG_SW_MGMT_TX to indicate that management
   7 frames need to be software encrypted. Since normal data packets are still
   8 encrypted by the hardware, crypto_tx_tailroom_needed_cnt gets decremented
   9 after key upload. This can lead to passing skbs to ccmp_encrypt_skb, which
  10 don't have the needed tailroom for software encryption.
  11
  12 Change the code to add tailroom for encrypted management packets, even if
  13 crypto_tx_tailroom_needed_cnt is 0.
  14
  15 Cc: stable@vger.kernel.org
  16 Signed-off-by: Felix Fietkau <nbd@nbd.name>
  17 ---
  18
  19 --- a/net/mac80211/tx.c
  20 +++ b/net/mac80211/tx.c
  21 @@ -1912,9 +1912,16 @@ static int ieee80211_skb_resize(struct i
  22                                 int head_need, bool may_encrypt)
  23  {
  24         struct ieee80211_local *local = sdata->local;
  25 +       struct ieee80211_hdr *hdr;
  26 +       bool enc_tailroom;
  27         int tail_need = 0;
  28
  29 -       if (may_encrypt && sdata->crypto_tx_tailroom_needed_cnt) {
  30 +       hdr = (struct ieee80211_hdr *) skb->data;
  31 +       enc_tailroom = may_encrypt &&
  32 +                      (sdata->crypto_tx_tailroom_needed_cnt ||
  33 +                       ieee80211_is_mgmt(hdr->frame_control));
  34 +
  35 +       if (enc_tailroom) {
  36                 tail_need = IEEE80211_ENCRYPT_TAILROOM;
  37                 tail_need -= skb_tailroom(skb);
  38                 tail_need = max_t(int, tail_need, 0);
  39 @@ -1922,8 +1929,7 @@ static int ieee80211_skb_resize(struct i
  40
  41         if (skb_cloned(skb) &&
  42             (!ieee80211_hw_check(&local->hw, SUPPORTS_CLONED_SKBS) ||
  43 -            !skb_clone_writable(skb, ETH_HLEN) ||
  44 -            (may_encrypt && sdata->crypto_tx_tailroom_needed_cnt)))
  45 +            !skb_clone_writable(skb, ETH_HLEN) || enc_tailroom))
  46                 I802_DEBUG_INC(local->tx_expand_skb_head_cloned);
  47         else if (head_need || tail_need)
  48                 I802_DEBUG_INC(local->tx_expand_skb_head);