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Subject[046/289] mac80211: fix possible null-pointer de-reference
2.6.36-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Christian Lamparter <chunkeey@googlemail.com>

commit d12c74528e3065c90df70fbc06ec6ffd6e804738 upstream.

This patch not only fixes a null-pointer de-reference
that would be triggered by a PLINK_OPEN frame with mis-
matching/incompatible mesh configuration, but also
responds correctly to non-compatible PLINK_OPEN frames
by generating a PLINK_CLOSE with the right reason code.

The original bug was detected by smatch.
( http://repo.or.cz/w/smatch.git )

net/mac80211/mesh_plink.c +574 mesh_rx_plink_frame(168)
error: we previously assumed 'sta' could be null.

Reviewed-and-Tested-by: Steve deRosier <steve@cozybit.com>
Reviewed-and-Tested-by: Javier Cardona <javier@cozybit.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
net/mac80211/mesh_plink.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
--- a/net/mac80211/mesh_plink.c
+++ b/net/mac80211/mesh_plink.c
@@ -412,7 +412,7 @@ void mesh_rx_plink_frame(struct ieee8021
enum plink_event event;
enum plink_frame_type ftype;
size_t baselen;
- bool deactivated;
+ bool deactivated, matches_local = true;
u8 ie_len;
u8 *baseaddr;
__le16 plid, llid, reason;
@@ -487,6 +487,7 @@ void mesh_rx_plink_frame(struct ieee8021
/* Now we will figure out the appropriate event... */
event = PLINK_UNDEFINED;
if (ftype != PLINK_CLOSE && (!mesh_matches_local(&elems, sdata))) {
+ matches_local = false;
switch (ftype) {
case PLINK_OPEN:
event = OPN_RJCT;
@@ -498,7 +499,15 @@ void mesh_rx_plink_frame(struct ieee8021
/* avoid warning */
break;
}
- spin_lock_bh(&sta->lock);
+ }
+
+ if (!sta && !matches_local) {
+ rcu_read_unlock();
+ reason = cpu_to_le16(MESH_CAPABILITY_POLICY_VIOLATION);
+ llid = 0;
+ mesh_plink_frame_tx(sdata, PLINK_CLOSE, mgmt->sa, llid,
+ plid, reason);
+ return;
} else if (!sta) {
/* ftype == PLINK_OPEN */
u32 rates;
@@ -522,7 +531,7 @@ void mesh_rx_plink_frame(struct ieee8021
}
event = OPN_ACPT;
spin_lock_bh(&sta->lock);
- } else {
+ } else if (matches_local) {
spin_lock_bh(&sta->lock);
switch (ftype) {
case PLINK_OPEN:
@@ -564,6 +573,8 @@ void mesh_rx_plink_frame(struct ieee8021
rcu_read_unlock();
return;
}
+ } else {
+ spin_lock_bh(&sta->lock);
}

mpl_dbg("Mesh plink (peer, state, llid, plid, event): %pM %s %d %d %d\n",



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