wimax/i2400m: fix oops caused by race condition when exiting USB kthreads

Current i2400m USB code had to threads (one for processing RX, one for
TX). When calling i2400m_{tx,rx}_release(), it would crash if the
thread had exited already due to an error.

So changed the code to have the thread fill in/out
i2400mu->{tx,rx}_kthread under a spinlock; then the _release()
function will call kthread_stop() only if {rx,tx}_kthread is still
set.

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>

diff --git a/drivers/net/wimax/i2400m/usb-rx.c b/drivers/net/wimax/i2400m/usb-rx.c
index e494e37..245587f 100644 (file)
--- a/drivers/net/wimax/i2400m/usb-rx.c
+++ b/drivers/net/wimax/i2400m/usb-rx.c
@@ -316,10 +316,15 @@ int i2400mu_rxd(void *_i2400mu)
        size_t pending;
        int rx_size;
        struct sk_buff *rx_skb;
+       unsigned long flags;
 
        d_fnstart(4, dev, "(i2400mu %p)\n", i2400mu);
+       spin_lock_irqsave(&i2400m->rx_lock, flags);
+       BUG_ON(i2400mu->rx_kthread != NULL);
+       i2400mu->rx_kthread = current;
+       spin_unlock_irqrestore(&i2400m->rx_lock, flags);
        while (1) {
-               d_printf(2, dev, "TX: waiting for messages\n");
+               d_printf(2, dev, "RX: waiting for messages\n");
                pending = 0;
                wait_event_interruptible(
                        i2400mu->rx_wq,
@@ -367,6 +372,9 @@ int i2400mu_rxd(void *_i2400mu)
        }
        result = 0;
 out:
+       spin_lock_irqsave(&i2400m->rx_lock, flags);
+       i2400mu->rx_kthread = NULL;
+       spin_unlock_irqrestore(&i2400m->rx_lock, flags);
        d_fnend(4, dev, "(i2400mu %p) = %d\n", i2400mu, result);
        return result;
 
@@ -403,18 +411,33 @@ int i2400mu_rx_setup(struct i2400mu *i2400mu)
        struct i2400m *i2400m = &i2400mu->i2400m;
        struct device *dev = &i2400mu->usb_iface->dev;
        struct wimax_dev *wimax_dev = &i2400m->wimax_dev;
+       struct task_struct *kthread;
 
-       i2400mu->rx_kthread = kthread_run(i2400mu_rxd, i2400mu, "%s-rx",
-                                         wimax_dev->name);
-       if (IS_ERR(i2400mu->rx_kthread)) {
-               result = PTR_ERR(i2400mu->rx_kthread);
+       kthread = kthread_run(i2400mu_rxd, i2400mu, "%s-rx",
+                             wimax_dev->name);
+       /* the kthread function sets i2400mu->rx_thread */
+       if (IS_ERR(kthread)) {
+               result = PTR_ERR(kthread);
                dev_err(dev, "RX: cannot start thread: %d\n", result);
        }
        return result;
 }
 
+
 void i2400mu_rx_release(struct i2400mu *i2400mu)
 {
-       kthread_stop(i2400mu->rx_kthread);
+       unsigned long flags;
+       struct i2400m *i2400m = &i2400mu->i2400m;
+       struct device *dev = i2400m_dev(i2400m);
+       struct task_struct *kthread;
+
+       spin_lock_irqsave(&i2400m->rx_lock, flags);
+       kthread = i2400mu->rx_kthread;
+       i2400mu->rx_kthread = NULL;
+       spin_unlock_irqrestore(&i2400m->rx_lock, flags);
+       if (kthread)
+               kthread_stop(kthread);
+       else
+               d_printf(1, dev, "RX: kthread had already exited\n");
 }
 

diff --git a/drivers/net/wimax/i2400m/usb-tx.c b/drivers/net/wimax/i2400m/usb-tx.c
index 90dfff1..a3c46e9 100644 (file)
--- a/drivers/net/wimax/i2400m/usb-tx.c
+++ b/drivers/net/wimax/i2400m/usb-tx.c
@@ -161,9 +161,15 @@ int i2400mu_txd(void *_i2400mu)
        struct device *dev = &i2400mu->usb_iface->dev;
        struct i2400m_msg_hdr *tx_msg;
        size_t tx_msg_size;
+       unsigned long flags;
 
        d_fnstart(4, dev, "(i2400mu %p)\n", i2400mu);
 
+       spin_lock_irqsave(&i2400m->tx_lock, flags);
+       BUG_ON(i2400mu->tx_kthread != NULL);
+       i2400mu->tx_kthread = current;
+       spin_unlock_irqrestore(&i2400m->tx_lock, flags);
+
        while (1) {
                d_printf(2, dev, "TX: waiting for messages\n");
                tx_msg = NULL;
@@ -183,6 +189,11 @@ int i2400mu_txd(void *_i2400mu)
                if (result < 0)
                        break;
        }
+
+       spin_lock_irqsave(&i2400m->tx_lock, flags);
+       i2400mu->tx_kthread = NULL;
+       spin_unlock_irqrestore(&i2400m->tx_lock, flags);
+
        d_fnend(4, dev, "(i2400mu %p) = %d\n", i2400mu, result);
        return result;
 }
@@ -213,11 +224,13 @@ int i2400mu_tx_setup(struct i2400mu *i2400mu)
        struct i2400m *i2400m = &i2400mu->i2400m;
        struct device *dev = &i2400mu->usb_iface->dev;
        struct wimax_dev *wimax_dev = &i2400m->wimax_dev;
+       struct task_struct *kthread;
 
-       i2400mu->tx_kthread = kthread_run(i2400mu_txd, i2400mu, "%s-tx",
-                                         wimax_dev->name);
-       if (IS_ERR(i2400mu->tx_kthread)) {
-               result = PTR_ERR(i2400mu->tx_kthread);
+       kthread = kthread_run(i2400mu_txd, i2400mu, "%s-tx",
+                             wimax_dev->name);
+       /* the kthread function sets i2400mu->tx_thread */
+       if (IS_ERR(kthread)) {
+               result = PTR_ERR(kthread);
                dev_err(dev, "TX: cannot start thread: %d\n", result);
        }
        return result;
@@ -225,5 +238,17 @@ int i2400mu_tx_setup(struct i2400mu *i2400mu)
 
 void i2400mu_tx_release(struct i2400mu *i2400mu)
 {
-       kthread_stop(i2400mu->tx_kthread);
+       unsigned long flags;
+       struct i2400m *i2400m = &i2400mu->i2400m;
+       struct device *dev = i2400m_dev(i2400m);
+       struct task_struct *kthread;
+
+       spin_lock_irqsave(&i2400m->tx_lock, flags);
+       kthread = i2400mu->tx_kthread;
+       i2400mu->tx_kthread = NULL;
+       spin_unlock_irqrestore(&i2400m->tx_lock, flags);
+       if (kthread)
+               kthread_stop(kthread);
+       else
+               d_printf(1, dev, "TX: kthread had already exited\n");
 }