mac80211: Skip tailroom reservation for full HW-crypto devices with race fix

Based on inputs from Johannes Berg <johannes@sipsolutions.net>
from http://article.gmane.org/gmane.linux.kernel.wireless.general/68193
and http://article.gmane.org/gmane.linux.kernel.wireless.general/71702

In xmit path, devices that do full hardware crypto (including
MMIC and ICV) need no tailroom. For such devices, tailroom
reservation can be skipped if all the keys are programmed into
the hardware (i.e software crypto is not used for any of the
keys) and none of the keys wants software to generate Michael
MIC and IV.

v2: Added check for IV along with MMIC.
Reported-by: Fabio Rossi <rossi.f@inwind.it>
Tested-by: Fabio Rossi <rossi.f@inwind.it>
Signed-off-by: Mohammed Shafi Shajakhan <mshajakhan@atheros.com>
Cc: Mohammed Shafi Shajakhan <mshajakhan@atheros.com>

v3: Fixing races to avoid WARNING: at net/mac80211/wpa.c:397
    ccmp_encrypt_skb+0xc4/0x1f0
Reported-by: Andreas Hartmann <andihartmann@01019freenet.de>
Tested-by: Andreas Hartmann <andihartmann@01019freenet.de>

v4: Added links with message ID

Signed-off-by: Yogesh Ashok Powar <yogeshp@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 5 insertions, 9 deletions

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 3104c844b544..e8d0d2d22665 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1474,18 +1474,14 @@ static bool ieee80211_tx(struct ieee80211_sub_if_data *sdata,
 
 /* device xmit handlers */
 
-static int ieee80211_skb_resize(struct ieee80211_local *local,
+static int ieee80211_skb_resize(struct ieee80211_sub_if_data *sdata,
                                 struct sk_buff *skb,
                                 int head_need, bool may_encrypt)
 {
+        struct ieee80211_local *local = sdata->local;
         int tail_need = 0;
 
-        /*
-         * This could be optimised, devices that do full hardware
-         * crypto (including TKIP MMIC) need no tailroom... But we
-         * have no drivers for such devices currently.
-         */
-        if (may_encrypt) {
+        if (may_encrypt && sdata->crypto_tx_tailroom_needed_cnt) {
                 tail_need = IEEE80211_ENCRYPT_TAILROOM;
                 tail_need -= skb_tailroom(skb);
                 tail_need = max_t(int, tail_need, 0);
@@ -1578,7 +1574,7 @@ static void ieee80211_xmit(struct ieee80211_sub_if_data *sdata,
         headroom -= skb_headroom(skb);
         headroom = max_t(int, 0, headroom);
 
-        if (ieee80211_skb_resize(local, skb, headroom, may_encrypt)) {
+        if (ieee80211_skb_resize(sdata, skb, headroom, may_encrypt)) {
                 dev_kfree_skb(skb);
                 rcu_read_unlock();
                 return;
@@ -1945,7 +1941,7 @@ netdev_tx_t ieee80211_subif_start_xmit(struct sk_buff *skb,
                 head_need += IEEE80211_ENCRYPT_HEADROOM;
                 head_need += local->tx_headroom;
                 head_need = max_t(int, 0, head_need);
-                if (ieee80211_skb_resize(local, skb, head_need, true))
+                if (ieee80211_skb_resize(sdata, skb, head_need, true))
                         goto fail;
         }