2013-06-12 20:20:20

by Ben Greear

Subject: [RFC] mac80211: Ensure tid_start_tx is protected by sta->lock.

From: Ben Greear <[email protected]>

I believe this is more correct, though it did not fix the
memory leak I was chasing when I found this code.

Signed-off-by: Ben Greear <[email protected]>
---
net/mac80211/ht.c | 5 ++++-
net/mac80211/sta_info.h | 1 +
2 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/net/mac80211/ht.c b/net/mac80211/ht.c
index 0db25d4..c6256b4 100644
--- a/net/mac80211/ht.c
+++ b/net/mac80211/ht.c
@@ -283,13 +283,14 @@ void ieee80211_ba_session_work(struct work_struct *work)
sta, tid, WLAN_BACK_RECIPIENT,
WLAN_REASON_UNSPECIFIED, true);

+ spin_lock_bh(&sta->lock);
+
tid_tx = sta->ampdu_mlme.tid_start_tx[tid];
if (tid_tx) {
/*
* Assign it over to the normal tid_tx array
* where it "goes live".
*/
- spin_lock_bh(&sta->lock);

sta->ampdu_mlme.tid_start_tx[tid] = NULL;
/* could there be a race? */
@@ -301,6 +302,8 @@ void ieee80211_ba_session_work(struct work_struct *work)

ieee80211_tx_ba_session_handle_start(sta, tid);
continue;
+ } else {
+ spin_unlock_bh(&sta->lock);
}

tid_tx = rcu_dereference_protected_tid_tx(sta, tid);
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index c509423..0f85418 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -204,6 +204,7 @@ struct tid_ampdu_rx {
* driver requested to close until the work for it runs
* @mtx: mutex to protect all TX data (except non-NULL assignments
* to tid_tx[idx], which are protected by the sta spinlock)
+ * tid_start_tx is also protected by sta->lock.
*/
struct sta_ampdu_mlme {
struct mutex mtx;
--
1.7.3.4

2013-06-12 20:47:15

by Johannes Berg

Subject: Re: [RFC] mac80211: Ensure tid_start_tx is protected by sta->lock.

On Wed, 2013-06-12 at 13:20 -0700, [email protected] wrote:

> I believe this is more correct, though it did not fix the
> memory leak I was chasing when I found this code.

That description could use some work :-)

> + spin_lock_bh(&sta->lock);
> +
> tid_tx = sta->ampdu_mlme.tid_start_tx[tid];
> if (tid_tx) {
> /*
> * Assign it over to the normal tid_tx array
> * where it "goes live".
> */
> - spin_lock_bh(&sta->lock);
>
> sta->ampdu_mlme.tid_start_tx[tid] = NULL;
> /* could there be a race? */
> @@ -301,6 +302,8 @@ void ieee80211_ba_session_work(struct work_struct *work)
>
> ieee80211_tx_ba_session_handle_start(sta, tid);
> continue;
> + } else {
> + spin_unlock_bh(&sta->lock);
> }
>

You could just put the unlock after the if block, given the continue in
it, I think I'd prefer that.

> tid_tx = rcu_dereference_protected_tid_tx(sta, tid);
> diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
> index c509423..0f85418 100644
> --- a/net/mac80211/sta_info.h
> +++ b/net/mac80211/sta_info.h
> @@ -204,6 +204,7 @@ struct tid_ampdu_rx {
> * driver requested to close until the work for it runs
> * @mtx: mutex to protect all TX data (except non-NULL assignments
> * to tid_tx[idx], which are protected by the sta spinlock)
> + * tid_start_tx is also protected by sta->lock.

That should be a tab.

johannes