From ba46ce30f13a13bb24d05e21df2571ad724f1a1e Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 13 Mar 2012 19:07:18 +0100 Subject: [PATCH] staging: usbip: fix the usage of kthread_stop() stub_shutdown_connection() and vhci_shutdown_connection() use task_is_dead() before kthread_stop(). This buys nothing and wrong. kthread_stop() is fine even if this thread is dead. However, if it is dead nothing protects this task_struct, we shouldn't touch this memory. Change the code to do the necessary get_task_struct/put_task_struct. This patch assumes that - xxx_shutdown_connection() is always called, so we can't leak the task_struct. - kthread_stop_put() can't be called twice on the same task. Signed-off-by: Oleg Nesterov Cc: Tobias Klauser Cc: Matt Mooney , Signed-off-by: Greg Kroah-Hartman --- drivers/staging/usbip/stub_dev.c | 12 ++++++------ drivers/staging/usbip/usbip_common.h | 17 +++++++++++++++++ drivers/staging/usbip/vhci_hcd.c | 8 ++++---- drivers/staging/usbip/vhci_sysfs.c | 4 ++-- 4 files changed, 29 insertions(+), 12 deletions(-) diff --git a/drivers/staging/usbip/stub_dev.c b/drivers/staging/usbip/stub_dev.c index fa870e3f7f6a..92ced35e6b7f 100644 --- a/drivers/staging/usbip/stub_dev.c +++ b/drivers/staging/usbip/stub_dev.c @@ -113,8 +113,8 @@ static ssize_t store_sockfd(struct device *dev, struct device_attribute *attr, spin_unlock(&sdev->ud.lock); - sdev->ud.tcp_rx = kthread_run(stub_rx_loop, &sdev->ud, "stub_rx"); - sdev->ud.tcp_tx = kthread_run(stub_tx_loop, &sdev->ud, "stub_tx"); + sdev->ud.tcp_rx = kthread_get_run(stub_rx_loop, &sdev->ud, "stub_rx"); + sdev->ud.tcp_tx = kthread_get_run(stub_tx_loop, &sdev->ud, "stub_tx"); spin_lock(&sdev->ud.lock); sdev->ud.status = SDEV_ST_USED; @@ -187,10 +187,10 @@ static void stub_shutdown_connection(struct usbip_device *ud) } /* 1. stop threads */ - if (ud->tcp_rx && !task_is_dead(ud->tcp_rx)) - kthread_stop(ud->tcp_rx); - if (ud->tcp_tx && !task_is_dead(ud->tcp_tx)) - kthread_stop(ud->tcp_tx); + if (ud->tcp_rx) + kthread_stop_put(ud->tcp_rx); + if (ud->tcp_tx) + kthread_stop_put(ud->tcp_tx); /* * 2. close the socket diff --git a/drivers/staging/usbip/usbip_common.h b/drivers/staging/usbip/usbip_common.h index c7b888ca54f5..5d89c0fd6f7b 100644 --- a/drivers/staging/usbip/usbip_common.h +++ b/drivers/staging/usbip/usbip_common.h @@ -292,6 +292,23 @@ struct usbip_device { } eh_ops; }; +#define kthread_get_run(threadfn, data, namefmt, ...) \ +({ \ + struct task_struct *__k \ + = kthread_create(threadfn, data, namefmt, ## __VA_ARGS__); \ + if (!IS_ERR(__k)) { \ + get_task_struct(__k); \ + wake_up_process(__k); \ + } \ + __k; \ +}) + +#define kthread_stop_put(k) \ + do { \ + kthread_stop(k); \ + put_task_struct(k); \ + } while (0) + /* usbip_common.c */ void usbip_dump_urb(struct urb *purb); void usbip_dump_header(struct usbip_header *pdu); diff --git a/drivers/staging/usbip/vhci_hcd.c b/drivers/staging/usbip/vhci_hcd.c index dca9bf11f0c2..f708cbaee16b 100644 --- a/drivers/staging/usbip/vhci_hcd.c +++ b/drivers/staging/usbip/vhci_hcd.c @@ -821,10 +821,10 @@ static void vhci_shutdown_connection(struct usbip_device *ud) } /* kill threads related to this sdev, if v.c. exists */ - if (vdev->ud.tcp_rx && !task_is_dead(vdev->ud.tcp_rx)) - kthread_stop(vdev->ud.tcp_rx); - if (vdev->ud.tcp_tx && !task_is_dead(vdev->ud.tcp_tx)) - kthread_stop(vdev->ud.tcp_tx); + if (vdev->ud.tcp_rx) + kthread_stop_put(vdev->ud.tcp_rx); + if (vdev->ud.tcp_tx) + kthread_stop_put(vdev->ud.tcp_tx); pr_info("stop threads\n"); diff --git a/drivers/staging/usbip/vhci_sysfs.c b/drivers/staging/usbip/vhci_sysfs.c index 0cd039bb5fd6..7ce9c2f7e442 100644 --- a/drivers/staging/usbip/vhci_sysfs.c +++ b/drivers/staging/usbip/vhci_sysfs.c @@ -222,8 +222,8 @@ static ssize_t store_attach(struct device *dev, struct device_attribute *attr, spin_unlock(&the_controller->lock); /* end the lock */ - vdev->ud.tcp_rx = kthread_run(vhci_rx_loop, &vdev->ud, "vhci_rx"); - vdev->ud.tcp_tx = kthread_run(vhci_tx_loop, &vdev->ud, "vhci_tx"); + vdev->ud.tcp_rx = kthread_get_run(vhci_rx_loop, &vdev->ud, "vhci_rx"); + vdev->ud.tcp_tx = kthread_get_run(vhci_tx_loop, &vdev->ud, "vhci_tx"); rh_port_connect(rhport, speed); -- 2.30.2