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Subject[PATCH 20/25] wimax/i2400m: fix i2400m->wake_tx_skb handling
Date
i2400m_net_wake_tx() sets ->wake_tx_skb with the given skb if
->wake_tx_ws is not pending; however, i2400m_wake_tx_work() could have
just started execution and haven't fetched -><wake_tx_skb yet. The
previous packet will be leaked.

Update ->wake_tx_skb handling.

* i2400m_net_wake_tx() now tests whether the previous ->wake_tx_skb
has been consumed by ->wake_tx_ws instead of testing work_pending().

* i2400m_net_wake_stop() is simplified similarly. It always puts
->wake_tx_skb if non-NULL.

* Spurious ->wake_tx_skb dereference outside critical section dropped
from i2400m_wake_tx_work().

Only compile tested.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
Cc: linux-wimax@intel.com
Cc: wimax@linuxwimax.org
---
Please let me know how this patch should be routed. I can take it
through the workqueue tree if necessary.

Thanks.

drivers/net/wimax/i2400m/netdev.c | 31 +++++++++++++++++--------------
1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/drivers/net/wimax/i2400m/netdev.c b/drivers/net/wimax/i2400m/netdev.c
index 1d76ae8..530581c 100644
--- a/drivers/net/wimax/i2400m/netdev.c
+++ b/drivers/net/wimax/i2400m/netdev.c
@@ -156,7 +156,7 @@ void i2400m_wake_tx_work(struct work_struct *ws)
struct i2400m *i2400m = container_of(ws, struct i2400m, wake_tx_ws);
struct net_device *net_dev = i2400m->wimax_dev.net_dev;
struct device *dev = i2400m_dev(i2400m);
- struct sk_buff *skb = i2400m->wake_tx_skb;
+ struct sk_buff *skb;
unsigned long flags;

spin_lock_irqsave(&i2400m->tx_lock, flags);
@@ -236,23 +236,26 @@ void i2400m_tx_prep_header(struct sk_buff *skb)
void i2400m_net_wake_stop(struct i2400m *i2400m)
{
struct device *dev = i2400m_dev(i2400m);
+ struct sk_buff *wake_tx_skb;
+ unsigned long flags;

d_fnstart(3, dev, "(i2400m %p)\n", i2400m);
- /* See i2400m_hard_start_xmit(), references are taken there
- * and here we release them if the work was still
- * pending. Note we can't differentiate work not pending vs
- * never scheduled, so the NULL check does that. */
- if (cancel_work_sync(&i2400m->wake_tx_ws) == 0
- && i2400m->wake_tx_skb != NULL) {
- unsigned long flags;
- struct sk_buff *wake_tx_skb;
- spin_lock_irqsave(&i2400m->tx_lock, flags);
- wake_tx_skb = i2400m->wake_tx_skb; /* compat help */
- i2400m->wake_tx_skb = NULL; /* compat help */
- spin_unlock_irqrestore(&i2400m->tx_lock, flags);
+ /*
+ * See i2400m_hard_start_xmit(), references are taken there and
+ * here we release them if the packet was still pending.
+ */
+ cancel_work_sync(&i2400m->wake_tx_ws);
+
+ spin_lock_irqsave(&i2400m->tx_lock, flags);
+ wake_tx_skb = i2400m->wake_tx_skb;
+ i2400m->wake_tx_skb = NULL;
+ spin_unlock_irqrestore(&i2400m->tx_lock, flags);
+
+ if (wake_tx_skb) {
i2400m_put(i2400m);
kfree_skb(wake_tx_skb);
}
+
d_fnend(3, dev, "(i2400m %p) = void\n", i2400m);
}

@@ -288,7 +291,7 @@ int i2400m_net_wake_tx(struct i2400m *i2400m, struct net_device *net_dev,
* and if pending, release those resources. */
result = 0;
spin_lock_irqsave(&i2400m->tx_lock, flags);
- if (!work_pending(&i2400m->wake_tx_ws)) {
+ if (!i2400m->wake_tx_skb) {
netif_stop_queue(net_dev);
i2400m_get(i2400m);
i2400m->wake_tx_skb = skb_get(skb); /* transfer ref count */
--
1.8.0.2


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