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Subject[PATCH 4.20 36/50] mac80211: ensure that mgmt tx skbs have tailroom for encryption
Date
4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Felix Fietkau <nbd@nbd.name>

commit 9d0f50b80222dc273e67e4e14410fcfa4130a90c upstream.

Some drivers use IEEE80211_KEY_FLAG_SW_MGMT_TX to indicate that management
frames need to be software encrypted. Since normal data packets are still
encrypted by the hardware, crypto_tx_tailroom_needed_cnt gets decremented
after key upload to hw. This can lead to passing skbs to ccmp_encrypt_skb,
which don't have the necessary tailroom for software encryption.

Change the code to add tailroom for encrypted management packets, even if
crypto_tx_tailroom_needed_cnt is 0.

Cc: stable@vger.kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/mac80211/tx.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1938,9 +1938,16 @@ static int ieee80211_skb_resize(struct i
int head_need, bool may_encrypt)
{
struct ieee80211_local *local = sdata->local;
+ struct ieee80211_hdr *hdr;
+ bool enc_tailroom;
int tail_need = 0;

- if (may_encrypt && sdata->crypto_tx_tailroom_needed_cnt) {
+ hdr = (struct ieee80211_hdr *) skb->data;
+ enc_tailroom = may_encrypt &&
+ (sdata->crypto_tx_tailroom_needed_cnt ||
+ ieee80211_is_mgmt(hdr->frame_control));
+
+ if (enc_tailroom) {
tail_need = IEEE80211_ENCRYPT_TAILROOM;
tail_need -= skb_tailroom(skb);
tail_need = max_t(int, tail_need, 0);
@@ -1948,8 +1955,7 @@ static int ieee80211_skb_resize(struct i

if (skb_cloned(skb) &&
(!ieee80211_hw_check(&local->hw, SUPPORTS_CLONED_SKBS) ||
- !skb_clone_writable(skb, ETH_HLEN) ||
- (may_encrypt && sdata->crypto_tx_tailroom_needed_cnt)))
+ !skb_clone_writable(skb, ETH_HLEN) || enc_tailroom))
I802_DEBUG_INC(local->tx_expand_skb_head_cloned);
else if (head_need || tail_need)
I802_DEBUG_INC(local->tx_expand_skb_head);

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