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From: Greg KH on 6 Aug 2010 14:40
2.6.35-stable review patch. If anyone has any objections, please let us know.

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

From: John W. Linville <linville(a)tuxdriver.com>

commit c937019761a758f2749b1f3a032b7a91fb044753 upstream.

While mesh_rx_plink_frame holds sta->lock...

mesh_rx_plink_frame ->
mesh_plink_inc_estab_count ->
ieee80211_bss_info_change_notify

....but ieee80211_bss_info_change_notify is allowed to sleep. A driver
taking advantage of that allowance can cause a scheduling while
atomic bug. Similar paths exist for mesh_plink_dec_estab_count,
so work around those as well.

http://bugzilla.kernel.org/show_bug.cgi?id=16099

Also, correct a minor kerneldoc comment error (mismatched function names).

Signed-off-by: John W. Linville <linville(a)tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh(a)suse.de>

---
net/mac80211/mesh_plink.c | 42 +++++++++++++++++++++++++++++++-----------
1 file changed, 31 insertions(+), 11 deletions(-)

--- a/net/mac80211/mesh_plink.c
+++ b/net/mac80211/mesh_plink.c
@@ -65,7 +65,6 @@ void mesh_plink_inc_estab_count(struct i
{
atomic_inc(&sdata->u.mesh.mshstats.estab_plinks);
mesh_accept_plinks_update(sdata);
- ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_BEACON);
}

static inline
@@ -73,7 +72,6 @@ void mesh_plink_dec_estab_count(struct i
{
atomic_dec(&sdata->u.mesh.mshstats.estab_plinks);
mesh_accept_plinks_update(sdata);
- ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_BEACON);
}

/**
@@ -115,7 +113,7 @@ static struct sta_info *mesh_plink_alloc
}

/**
- * mesh_plink_deactivate - deactivate mesh peer link
+ * __mesh_plink_deactivate - deactivate mesh peer link
*
* @sta: mesh peer link to deactivate
*
@@ -123,18 +121,23 @@ static struct sta_info *mesh_plink_alloc
*
* Locking: the caller must hold sta->lock
*/
-static void __mesh_plink_deactivate(struct sta_info *sta)
+static bool __mesh_plink_deactivate(struct sta_info *sta)
{
struct ieee80211_sub_if_data *sdata = sta->sdata;
+ bool deactivated = false;

- if (sta->plink_state == PLINK_ESTAB)
+ if (sta->plink_state == PLINK_ESTAB) {
mesh_plink_dec_estab_count(sdata);
+ deactivated = true;
+ }
sta->plink_state = PLINK_BLOCKED;
mesh_path_flush_by_nexthop(sta);
+
+ return deactivated;
}

/**
- * __mesh_plink_deactivate - deactivate mesh peer link
+ * mesh_plink_deactivate - deactivate mesh peer link
*
* @sta: mesh peer link to deactivate
*
@@ -142,9 +145,15 @@ static void __mesh_plink_deactivate(stru
*/
void mesh_plink_deactivate(struct sta_info *sta)
{
+ struct ieee80211_sub_if_data *sdata = sta->sdata;
+ bool deactivated;
+
spin_lock_bh(&sta->lock);
- __mesh_plink_deactivate(sta);
+ deactivated = __mesh_plink_deactivate(sta);
spin_unlock_bh(&sta->lock);
+
+ if (deactivated)
+ ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_BEACON);
}

static int mesh_plink_frame_tx(struct ieee80211_sub_if_data *sdata,
@@ -381,10 +390,16 @@ int mesh_plink_open(struct sta_info *sta

void mesh_plink_block(struct sta_info *sta)
{
+ struct ieee80211_sub_if_data *sdata = sta->sdata;
+ bool deactivated;
+
spin_lock_bh(&sta->lock);
- __mesh_plink_deactivate(sta);
+ deactivated = __mesh_plink_deactivate(sta);
sta->plink_state = PLINK_BLOCKED;
spin_unlock_bh(&sta->lock);
+
+ if (deactivated)
+ ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_BEACON);
}


@@ -397,6 +412,7 @@ void mesh_rx_plink_frame(struct ieee8021
enum plink_event event;
enum plink_frame_type ftype;
size_t baselen;
+ bool deactivated;
u8 ie_len;
u8 *baseaddr;
__le16 plid, llid, reason;
@@ -651,8 +667,9 @@ void mesh_rx_plink_frame(struct ieee8021
case CNF_ACPT:
del_timer(&sta->plink_timer);
sta->plink_state = PLINK_ESTAB;
- mesh_plink_inc_estab_count(sdata);
spin_unlock_bh(&sta->lock);
+ mesh_plink_inc_estab_count(sdata);
+ ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_BEACON);
mpl_dbg("Mesh plink with %pM ESTABLISHED\n",
sta->sta.addr);
break;
@@ -684,8 +701,9 @@ void mesh_rx_plink_frame(struct ieee8021
case OPN_ACPT:
del_timer(&sta->plink_timer);
sta->plink_state = PLINK_ESTAB;
- mesh_plink_inc_estab_count(sdata);
spin_unlock_bh(&sta->lock);
+ mesh_plink_inc_estab_count(sdata);
+ ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_BEACON);
mpl_dbg("Mesh plink with %pM ESTABLISHED\n",
sta->sta.addr);
mesh_plink_frame_tx(sdata, PLINK_CONFIRM, sta->sta.addr, llid,
@@ -702,11 +720,13 @@ void mesh_rx_plink_frame(struct ieee8021
case CLS_ACPT:
reason = cpu_to_le16(MESH_CLOSE_RCVD);
sta->reason = reason;
- __mesh_plink_deactivate(sta);
+ deactivated = __mesh_plink_deactivate(sta);
sta->plink_state = PLINK_HOLDING;
llid = sta->llid;
mod_plink_timer(sta, dot11MeshHoldingTimeout(sdata));
spin_unlock_bh(&sta->lock);
+ if (deactivated)
+ ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_BEACON);
mesh_plink_frame_tx(sdata, PLINK_CLOSE, sta->sta.addr, llid,
plid, reason);
break;


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