mac80211: fix CCMP races

Since we can process multiple packets at the
same time for different ACs, but the PN is
allocated from a single counter, we need to
use an atomic value there. Use atomic64_t to
make this cheaper on 64-bit platforms, other
platforms will support this through software
emulation, see lib/atomic64.c.

We also need to use an on-stack scratch buf
so that multiple packets won't corrupt each
others scratch buffers.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 19 insertions, 13 deletions

diff --git a/net/mac80211/wpa.c b/net/mac80211/wpa.c
index 4ded2ae48a5f..7691e4edc74a 100644
--- a/net/mac80211/wpa.c
+++ b/net/mac80211/wpa.c
@@ -15,6 +15,7 @@
 #include <linux/gfp.h>
 #include <asm/unaligned.h>
 #include <net/mac80211.h>
+#include <crypto/aes.h>
 
 #include "ieee80211_i.h"
 #include "michael.h"
@@ -290,6 +291,8 @@ static void ccmp_special_blocks(struct sk_buff *skb, u8 *pn, u8 *scratch,
         unsigned int hdrlen;
         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 
+        memset(scratch, 0, 6 * AES_BLOCK_LEN);
+
         b_0 = scratch + 3 * AES_BLOCK_LEN;
         aad = scratch + 4 * AES_BLOCK_LEN;
 
@@ -380,8 +383,10 @@ static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
         struct ieee80211_key *key = tx->key;
         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
         int hdrlen, len, tail;
-        u8 *pos, *pn;
-        int i;
+        u8 *pos;
+        u8 pn[6];
+        u64 pn64;
+        u8 scratch[6 * AES_BLOCK_LEN];
 
         if (info->control.hw_key &&
             !(info->control.hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV)) {
@@ -409,14 +414,14 @@ static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
         hdr = (struct ieee80211_hdr *) pos;
         pos += hdrlen;
 
-        /* PN = PN + 1 */
-        pn = key->u.ccmp.tx_pn;
+        pn64 = atomic64_inc_return(&key->u.ccmp.tx_pn);
 
-        for (i = CCMP_PN_LEN - 1; i >= 0; i--) {
-                pn[i]++;
-                if (pn[i])
-                        break;
-        }
+        pn[5] = pn64;
+        pn[4] = pn64 >> 8;
+        pn[3] = pn64 >> 16;
+        pn[2] = pn64 >> 24;
+        pn[1] = pn64 >> 32;
+        pn[0] = pn64 >> 40;
 
         ccmp_pn2hdr(pos, pn, key->conf.keyidx);
 
@@ -425,8 +430,8 @@ static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
                 return 0;
 
         pos += CCMP_HDR_LEN;
-        ccmp_special_blocks(skb, pn, key->u.ccmp.tx_crypto_buf, 0);
-        ieee80211_aes_ccm_encrypt(key->u.ccmp.tfm, key->u.ccmp.tx_crypto_buf, pos, len,
+        ccmp_special_blocks(skb, pn, scratch, 0);
+        ieee80211_aes_ccm_encrypt(key->u.ccmp.tfm, scratch, pos, len,
                                   pos, skb_put(skb, CCMP_MIC_LEN));
 
         return 0;
@@ -482,11 +487,12 @@ ieee80211_crypto_ccmp_decrypt(struct ieee80211_rx_data *rx)
         }
 
         if (!(status->flag & RX_FLAG_DECRYPTED)) {
+                u8 scratch[6 * AES_BLOCK_LEN];
                 /* hardware didn't decrypt/verify MIC */
-                ccmp_special_blocks(skb, pn, key->u.ccmp.rx_crypto_buf, 1);
+                ccmp_special_blocks(skb, pn, scratch, 1);
 
                 if (ieee80211_aes_ccm_decrypt(
-                            key->u.ccmp.tfm, key->u.ccmp.rx_crypto_buf,
+                            key->u.ccmp.tfm, scratch,
                             skb->data + hdrlen + CCMP_HDR_LEN, data_len,
                             skb->data + skb->len - CCMP_MIC_LEN,
                             skb->data + hdrlen + CCMP_HDR_LEN))