From d11a6e4495ee1fbb38b59bc88d49d050d3736929 Mon Sep 17 00:00:00 2001 From: "Prasanna S. Panchamukhi" Date: Tue, 13 Apr 2010 16:35:58 -0700 Subject: [PATCH] wimax i2400m: fix race condition while accessing rx_roq by using kref count This patch fixes the race condition when one thread tries to destroy the memory allocated for rx_roq, while another thread still happen to access rx_roq. Such a race condition occurs when i2400m-sdio kernel module gets unloaded, destroying the memory allocated for rx_roq while rx_roq is accessed by i2400m_rx_edata(), as explained below: $thread1 $thread2 $ void i2400m_rx_edata() $ $Access rx_roq[] $ $roq = &i2400m->rx_roq[ro_cin] $ $ i2400m_roq_[reset/queue/update_ws] $ $ $ void i2400m_rx_release(); $ $kfree(rx->roq); $ $rx->roq = NULL; $Oops! rx_roq is NULL This patch fixes the race condition using refcount approach. Signed-off-by: Prasanna S. Panchamukhi --- drivers/net/wimax/i2400m/i2400m.h | 12 ++++++--- drivers/net/wimax/i2400m/rx.c | 44 +++++++++++++++++++++++++++---- 2 files changed, 48 insertions(+), 8 deletions(-) diff --git a/drivers/net/wimax/i2400m/i2400m.h b/drivers/net/wimax/i2400m/i2400m.h index 7a9c2c5b25cb..b8c7dbfead49 100644 --- a/drivers/net/wimax/i2400m/i2400m.h +++ b/drivers/net/wimax/i2400m/i2400m.h @@ -412,7 +412,7 @@ struct i2400m_barker_db; * * @tx_size_max: biggest TX message sent. * - * @rx_lock: spinlock to protect RX members + * @rx_lock: spinlock to protect RX members and rx_roq_refcount. * * @rx_pl_num: total number of payloads received * @@ -436,6 +436,10 @@ struct i2400m_barker_db; * delivered. Then the driver can release them to the host. See * drivers/net/i2400m/rx.c for details. * + * @rx_roq_refcount: refcount rx_roq. This refcounts any access to + * rx_roq thus preventing rx_roq being destroyed when rx_roq + * is being accessed. rx_roq_refcount is protected by rx_lock. + * * @rx_reports: reports received from the device that couldn't be * processed because the driver wasn't still ready; when ready, * they are pulled from here and chewed. @@ -597,10 +601,12 @@ struct i2400m { tx_num, tx_size_acc, tx_size_min, tx_size_max; /* RX stuff */ - spinlock_t rx_lock; /* protect RX state */ + /* protect RX state and rx_roq_refcount */ + spinlock_t rx_lock; unsigned rx_pl_num, rx_pl_max, rx_pl_min, rx_num, rx_size_acc, rx_size_min, rx_size_max; - struct i2400m_roq *rx_roq; /* not under rx_lock! */ + struct i2400m_roq *rx_roq; /* access is refcounted */ + struct kref rx_roq_refcount; /* refcount access to rx_roq */ u8 src_mac_addr[ETH_HLEN]; struct list_head rx_reports; /* under rx_lock! */ struct work_struct rx_report_ws; diff --git a/drivers/net/wimax/i2400m/rx.c b/drivers/net/wimax/i2400m/rx.c index fa2e11e5b4b9..71b697f3a68d 100644 --- a/drivers/net/wimax/i2400m/rx.c +++ b/drivers/net/wimax/i2400m/rx.c @@ -916,6 +916,25 @@ void i2400m_roq_queue_update_ws(struct i2400m *i2400m, struct i2400m_roq *roq, } +/* + * This routine destroys the memory allocated for rx_roq, when no + * other thread is accessing it. Access to rx_roq is refcounted by + * rx_roq_refcount, hence memory allocated must be destroyed when + * rx_roq_refcount becomes zero. This routine gets executed when + * rx_roq_refcount becomes zero. + */ +void i2400m_rx_roq_destroy(struct kref *ref) +{ + unsigned itr; + struct i2400m *i2400m + = container_of(ref, struct i2400m, rx_roq_refcount); + for (itr = 0; itr < I2400M_RO_CIN + 1; itr++) + __skb_queue_purge(&i2400m->rx_roq[itr].queue); + kfree(i2400m->rx_roq[0].log); + kfree(i2400m->rx_roq); + i2400m->rx_roq = NULL; +} + /* * Receive and send up an extended data packet * @@ -969,6 +988,7 @@ void i2400m_rx_edata(struct i2400m *i2400m, struct sk_buff *skb_rx, unsigned ro_needed, ro_type, ro_cin, ro_sn; struct i2400m_roq *roq; struct i2400m_roq_data *roq_data; + unsigned long flags; BUILD_BUG_ON(ETH_HLEN > sizeof(*hdr)); @@ -1007,7 +1027,16 @@ void i2400m_rx_edata(struct i2400m *i2400m, struct sk_buff *skb_rx, ro_cin = (reorder >> I2400M_RO_CIN_SHIFT) & I2400M_RO_CIN; ro_sn = (reorder >> I2400M_RO_SN_SHIFT) & I2400M_RO_SN; + spin_lock_irqsave(&i2400m->rx_lock, flags); roq = &i2400m->rx_roq[ro_cin]; + if (roq == NULL) { + kfree_skb(skb); /* rx_roq is already destroyed */ + spin_unlock_irqrestore(&i2400m->rx_lock, flags); + goto error; + } + kref_get(&i2400m->rx_roq_refcount); + spin_unlock_irqrestore(&i2400m->rx_lock, flags); + roq_data = (struct i2400m_roq_data *) &skb->cb; roq_data->sn = ro_sn; roq_data->cs = cs; @@ -1034,6 +1063,10 @@ void i2400m_rx_edata(struct i2400m *i2400m, struct sk_buff *skb_rx, default: dev_err(dev, "HW BUG? unknown reorder type %u\n", ro_type); } + + spin_lock_irqsave(&i2400m->rx_lock, flags); + kref_put(&i2400m->rx_roq_refcount, i2400m_rx_roq_destroy); + spin_unlock_irqrestore(&i2400m->rx_lock, flags); } else i2400m_net_erx(i2400m, skb, cs); @@ -1344,6 +1377,7 @@ int i2400m_rx_setup(struct i2400m *i2400m) __i2400m_roq_init(&i2400m->rx_roq[itr]); i2400m->rx_roq[itr].log = &rd[itr]; } + kref_init(&i2400m->rx_roq_refcount); } return 0; @@ -1357,12 +1391,12 @@ error_roq_alloc: /* Tear down the RX queue and infrastructure */ void i2400m_rx_release(struct i2400m *i2400m) { + unsigned long flags; + if (i2400m->rx_reorder) { - unsigned itr; - for(itr = 0; itr < I2400M_RO_CIN + 1; itr++) - __skb_queue_purge(&i2400m->rx_roq[itr].queue); - kfree(i2400m->rx_roq[0].log); - kfree(i2400m->rx_roq); + spin_lock_irqsave(&i2400m->rx_lock, flags); + kref_put(&i2400m->rx_roq_refcount, i2400m_rx_roq_destroy); + spin_unlock_irqrestore(&i2400m->rx_lock, flags); } /* at this point, nothing can be received... */ i2400m_report_hook_flush(i2400m);