2011-06-22 21:00:30

by Arik Nemtsov

Subject: [PATCH v2] mac80211: fix rx->key NULL dereference during mic failure

Sometimes when reporting a MIC failure rx->key may be unset. This
code path is hit when receiving a packet meant for a multicast
address, and decryption is performed in HW.

Fortunately, the failing key_idx is not used for anything up to
(and including) usermode, so we allow ourselves to drop it on the
way up when a key cannot be retrieved.

Signed-off-by: Arik Nemtsov <[email protected]>
---
include/net/cfg80211.h | 2 +-
net/mac80211/wpa.c | 8 +++++++-
net/wireless/nl80211.c | 3 ++-
3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 727131b..53be73e 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -2687,7 +2687,7 @@ void cfg80211_send_unprot_disassoc(struct net_device *dev, const u8 *buf,
* @dev: network device
* @addr: The source MAC address of the frame
* @key_type: The key type that the received frame used
- * @key_id: Key identifier (0..3)
+ * @key_id: Key identifier (0..3). Can be -1 if missing.
* @tsc: The TSC value of the frame that generated the MIC failure (6 octets)
* @gfp: allocation flags
*
diff --git a/net/mac80211/wpa.c b/net/mac80211/wpa.c
index 9dc3b5f..d91c1a2 100644
--- a/net/mac80211/wpa.c
+++ b/net/mac80211/wpa.c
@@ -154,7 +154,13 @@ update_iv:
return RX_CONTINUE;

mic_fail:
- mac80211_ev_michael_mic_failure(rx->sdata, rx->key->conf.keyidx,
+ /*
+ * In some cases the key can be unset - e.g. a multicast packet, in
+ * a driver that supports HW encryption. Send up the key idx only if
+ * the key is set.
+ */
+ mac80211_ev_michael_mic_failure(rx->sdata,
+ rx->key ? rx->key->conf.keyidx : -1,
(void *) skb->data, NULL, GFP_ATOMIC);
return RX_DROP_UNUSABLE;
}
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index ec83f41..785549d 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -6464,7 +6464,8 @@ void nl80211_michael_mic_failure(struct cfg80211_registered_device *rdev,
if (addr)
NLA_PUT(msg, NL80211_ATTR_MAC, ETH_ALEN, addr);
NLA_PUT_U32(msg, NL80211_ATTR_KEY_TYPE, key_type);
- NLA_PUT_U8(msg, NL80211_ATTR_KEY_IDX, key_id);
+ if (key_id != -1)
+ NLA_PUT_U8(msg, NL80211_ATTR_KEY_IDX, key_id);
if (tsc)
NLA_PUT(msg, NL80211_ATTR_KEY_SEQ, 6, tsc);

--
1.7.4.1

2011-06-22 21:03:50

by Johannes Berg

Subject: Re: [PATCH v2] mac80211: fix rx->key NULL dereference during mic failure

On Thu, 2011-06-23 at 00:00 +0300, Arik Nemtsov wrote:
> Sometimes when reporting a MIC failure rx->key may be unset. This
> code path is hit when receiving a packet meant for a multicast
> address, and decryption is performed in HW.
>
> Fortunately, the failing key_idx is not used for anything up to
> (and including) usermode, so we allow ourselves to drop it on the
> way up when a key cannot be retrieved.
>
> Signed-off-by: Arik Nemtsov <[email protected]>

Thanks. Since it fixes a crash, should it be Cc: [email protected]?

johannes