[PATCH 3.19.y-ckt 086/146] mac80211: move WEP tailroom size check

[Kamal Mostafa <kamal@canonical.com>]

3.19.8-ckt2 -stable review patch.  If anyone has any objections, please let me know.

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

From: Janusz Dziedzic <janusz.dziedzic@tieto.com>

commit 47b4e1fc4972cc43a19121bc2608a60aef3bf216 upstream.

Remove checking tailroom when adding IV as it uses only
headroom, and move the check to the ICV generation that
actually needs the tailroom.

In other case I hit such warning and datapath don't work,
when testing:
- IBSS + WEP
- ath9k with hw crypt enabled
- IPv6 data (ping6)

WARNING: CPU: 3 PID: 13301 at net/mac80211/wep.c:102 ieee80211_wep_add_iv+0x129/0x190 [mac80211]()
[...]
Call Trace:
[<ffffffff817bf491>] dump_stack+0x45/0x57
[<ffffffff8107746a>] warn_slowpath_common+0x8a/0xc0
[<ffffffff8107755a>] warn_slowpath_null+0x1a/0x20
[<ffffffffc09ae109>] ieee80211_wep_add_iv+0x129/0x190 [mac80211]
[<ffffffffc09ae7ab>] ieee80211_crypto_wep_encrypt+0x6b/0xd0 [mac80211]
[<ffffffffc09d3fb1>] invoke_tx_handlers+0xc51/0xf30 [mac80211]
[...]

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 net/mac80211/wep.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/mac80211/wep.c b/net/mac80211/wep.c
index a4220e9..efa3f48 100644
--- a/net/mac80211/wep.c
+++ b/net/mac80211/wep.c
@@ -98,8 +98,7 @@ static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
 
 	hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
 
-	if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN ||
-		    skb_headroom(skb) < IEEE80211_WEP_IV_LEN))
+	if (WARN_ON(skb_headroom(skb) < IEEE80211_WEP_IV_LEN))
 		return NULL;
 
 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
@@ -167,6 +166,9 @@ int ieee80211_wep_encrypt(struct ieee80211_local *local,
 	size_t len;
 	u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
 
+	if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN))
+		return -1;
+
 	iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx);
 	if (!iv)
 		return -1;
-- 
1.9.1