/* * Copyright (C) 2003-2008 Takahiro Hirofuchi * Copyright (C) 2015 Nobuo Iwata * * This is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, * USA. */ #include #include #include #include #include "usbip_common.h" struct usbip_event { struct list_head node; struct usbip_device *ud; }; static DEFINE_SPINLOCK(event_lock); static LIST_HEAD(event_list); static void set_event(struct usbip_device *ud, unsigned long event) { unsigned long flags; spin_lock_irqsave(&ud->lock, flags); ud->event |= event; spin_unlock_irqrestore(&ud->lock, flags); } static void unset_event(struct usbip_device *ud, unsigned long event) { unsigned long flags; spin_lock_irqsave(&ud->lock, flags); ud->event &= ~event; spin_unlock_irqrestore(&ud->lock, flags); } static struct usbip_device *get_event(void) { struct usbip_event *ue = NULL; struct usbip_device *ud = NULL; unsigned long flags; spin_lock_irqsave(&event_lock, flags); if (!list_empty(&event_list)) { ue = list_first_entry(&event_list, struct usbip_event, node); list_del(&ue->node); } spin_unlock_irqrestore(&event_lock, flags); if (ue) { ud = ue->ud; kfree(ue); } return ud; } static struct task_struct *worker_context; static void event_handler(struct work_struct *work) { struct usbip_device *ud; if (worker_context == NULL) { worker_context = current; } while ((ud = get_event()) != NULL) { usbip_dbg_eh("pending event %lx\n", ud->event); /* * NOTE: shutdown must come first. * Shutdown the device. */ if (ud->event & USBIP_EH_SHUTDOWN) { ud->eh_ops.shutdown(ud); unset_event(ud, USBIP_EH_SHUTDOWN); } /* Reset the device. */ if (ud->event & USBIP_EH_RESET) { ud->eh_ops.reset(ud); unset_event(ud, USBIP_EH_RESET); } /* Mark the device as unusable. */ if (ud->event & USBIP_EH_UNUSABLE) { ud->eh_ops.unusable(ud); unset_event(ud, USBIP_EH_UNUSABLE); } /* Stop the error handler. */ if (ud->event & USBIP_EH_BYE) usbip_dbg_eh("removed %p\n", ud); wake_up(&ud->eh_waitq); } } int usbip_start_eh(struct usbip_device *ud) { init_waitqueue_head(&ud->eh_waitq); ud->event = 0; return 0; } EXPORT_SYMBOL_GPL(usbip_start_eh); void usbip_stop_eh(struct usbip_device *ud) { unsigned long pending = ud->event & ~USBIP_EH_BYE; if (!(ud->event & USBIP_EH_BYE)) usbip_dbg_eh("usbip_eh stopping but not removed\n"); if (pending) usbip_dbg_eh("usbip_eh waiting completion %lx\n", pending); wait_event_interruptible(ud->eh_waitq, !(ud->event & ~USBIP_EH_BYE)); usbip_dbg_eh("usbip_eh has stopped\n"); } EXPORT_SYMBOL_GPL(usbip_stop_eh); #define WORK_QUEUE_NAME "usbip_event" static struct workqueue_struct *usbip_queue; static DECLARE_WORK(usbip_work, event_handler); int usbip_init_eh(void) { usbip_queue = create_singlethread_workqueue(WORK_QUEUE_NAME); if (usbip_queue == NULL) { pr_err("failed to create usbip_event\n"); return -ENOMEM; } return 0; } void usbip_finish_eh(void) { flush_workqueue(usbip_queue); destroy_workqueue(usbip_queue); usbip_queue = NULL; } void usbip_event_add(struct usbip_device *ud, unsigned long event) { struct usbip_event *ue; unsigned long flags; if (ud->event & USBIP_EH_BYE) return; set_event(ud, event); spin_lock_irqsave(&event_lock, flags); list_for_each_entry_reverse(ue, &event_list, node) { if (ue->ud == ud) goto out; } ue = kmalloc(sizeof(struct usbip_event), GFP_ATOMIC); if (ue == NULL) goto out; ue->ud = ud; list_add_tail(&ue->node, &event_list); queue_work(usbip_queue, &usbip_work); out: spin_unlock_irqrestore(&event_lock, flags); } EXPORT_SYMBOL_GPL(usbip_event_add); int usbip_event_happened(struct usbip_device *ud) { int happened = 0; unsigned long flags; spin_lock_irqsave(&ud->lock, flags); if (ud->event != 0) happened = 1; spin_unlock_irqrestore(&ud->lock, flags); return happened; } EXPORT_SYMBOL_GPL(usbip_event_happened); int usbip_in_eh(struct task_struct *task) { if (task == worker_context) return 1; return 0; } EXPORT_SYMBOL_GPL(usbip_in_eh); .vnet.ibm.com>2017-01-28 06:42:20 -0600 committerTejun Heo <tj@kernel.org>2017-01-28 07:49:42 -0500 commit966d2b04e070bc040319aaebfec09e0144dc3341 (patch) tree4b96156e3d1dd4dfd6039b7c219c9dc4616da52d /drivers/usb/dwc3/core.h parent1b1bc42c1692e9b62756323c675a44cb1a1f9dbd (diff)
percpu-refcount: fix reference leak during percpu-atomic transition
percpu_ref_tryget() and percpu_ref_tryget_live() should return "true" IFF they acquire a reference. But the return value from atomic_long_inc_not_zero() is a long and may have high bits set, e.g. PERCPU_COUNT_BIAS, and the return value of the tryget routines is bool so the reference may actually be acquired but the routines return "false" which results in a reference leak since the caller assumes it does not need to do a corresponding percpu_ref_put(). This was seen when performing CPU hotplug during I/O, as hangs in blk_mq_freeze_queue_wait where percpu_ref_kill (blk_mq_freeze_queue_start) raced with percpu_ref_tryget (blk_mq_timeout_work). Sample stack trace: __switch_to+0x2c0/0x450 __schedule+0x2f8/0x970 schedule+0x48/0xc0 blk_mq_freeze_queue_wait+0x94/0x120 blk_mq_queue_reinit_work+0xb8/0x180 blk_mq_queue_reinit_prepare+0x84/0xa0 cpuhp_invoke_callback+0x17c/0x600 cpuhp_up_callbacks+0x58/0x150 _cpu_up+0xf0/0x1c0 do_cpu_up+0x120/0x150 cpu_subsys_online+0x64/0xe0 device_online+0xb4/0x120 online_store+0xb4/0xc0 dev_attr_store+0x68/0xa0 sysfs_kf_write+0x80/0xb0 kernfs_fop_write+0x17c/0x250 __vfs_write+0x6c/0x1e0 vfs_write+0xd0/0x270 SyS_write+0x6c/0x110 system_call+0x38/0xe0 Examination of the queue showed a single reference (no PERCPU_COUNT_BIAS, and __PERCPU_REF_DEAD, __PERCPU_REF_ATOMIC set) and no requests. However, conditions at the time of the race are count of PERCPU_COUNT_BIAS + 0 and __PERCPU_REF_DEAD and __PERCPU_REF_ATOMIC set. The fix is to make the tryget routines use an actual boolean internally instead of the atomic long result truncated to a int. Fixes: e625305b3907 percpu-refcount: make percpu_ref based on longs instead of ints Link: https://bugzilla.kernel.org/show_bug.cgi?id=190751 Signed-off-by: Douglas Miller <dougmill@linux.vnet.ibm.com> Reviewed-by: Jens Axboe <axboe@fb.com> Signed-off-by: Tejun Heo <tj@kernel.org> Fixes: e625305b3907 ("percpu-refcount: make percpu_ref based on longs instead of ints") Cc: stable@vger.kernel.org # v3.18+
Diffstat (limited to 'drivers/usb/dwc3/core.h')