[PATCH v2 1/2] wifi: mac80211: fix encryption tailroom

[Chien Wong <m@xv97.com>]

BIP-CMAC-256 and BIP-GMAC append a 26-byte MME but mac80211
currently reserves only 18 bytes of encryption tailroom.

Generating 26-byte MME may happen to work because the actual skb
tailroom can exceed the requested amount. For example, dev_alloc_skb()
rounds the allocation to kmalloc size buckets or alignment boundaries,
and the extra space may cover the 8-byte shortfall.

Reserve enough tailroom for the 26-byte MME.

Fixes: 56c52da2d554 ("mac80111: Add BIP-CMAC-256 cipher")
Signed-off-by: Chien Wong <m@xv97.com>
---
 net/mac80211/ieee80211_i.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 9374c2942489..e3e66d05519e 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -52,7 +52,7 @@ struct ieee80211_mesh_fast_tx;
 
 /* Required encryption head and tailroom */
 #define IEEE80211_ENCRYPT_HEADROOM 8
-#define IEEE80211_ENCRYPT_TAILROOM 18
+#define IEEE80211_ENCRYPT_TAILROOM 26 /* current max: GMAC/CMAC-256 MME */
 
 /* power level hasn't been configured (or set to automatic) */
 #define IEEE80211_UNSET_POWER_LEVEL	INT_MIN
-- 
2.56.0