linux/drivers/usb/mon/mon_main.c
Arjan van de Ven bb4e3b5ac8 usbmon: fix tiny race exposed by the fastboot patches
usbmon registers the notifier chain, takes the bus lock and then goes to
scan the existing devices for hooking up.

Unfortunately, if usb_mon gets initialized while USB bus discovery is
going on, it's possible that usbmon gets a notifier on one cpu (which runs
without USB locks), and the scan is going on and also finds the new bus,
resulting in a double sysfs registration, which then produces a WARNING.

Pete Zaitcev did the bug diagnostics on this one

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2008-10-17 14:40:57 -07:00

433 lines
9.1 KiB
C

/*
* The USB Monitor, inspired by Dave Harding's USBMon.
*
* mon_main.c: Main file, module initiation and exit, registrations, etc.
*
* Copyright (C) 2005 Pete Zaitcev (zaitcev@redhat.com)
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/usb.h>
#include <linux/notifier.h>
#include <linux/mutex.h>
#include "usb_mon.h"
#include "../core/hcd.h"
static void mon_stop(struct mon_bus *mbus);
static void mon_dissolve(struct mon_bus *mbus, struct usb_bus *ubus);
static void mon_bus_drop(struct kref *r);
static void mon_bus_init(struct usb_bus *ubus);
DEFINE_MUTEX(mon_lock);
struct mon_bus mon_bus0; /* Pseudo bus meaning "all buses" */
static LIST_HEAD(mon_buses); /* All buses we know: struct mon_bus */
/*
* Link a reader into the bus.
*
* This must be called with mon_lock taken because of mbus->ref.
*/
void mon_reader_add(struct mon_bus *mbus, struct mon_reader *r)
{
unsigned long flags;
struct list_head *p;
spin_lock_irqsave(&mbus->lock, flags);
if (mbus->nreaders == 0) {
if (mbus == &mon_bus0) {
list_for_each (p, &mon_buses) {
struct mon_bus *m1;
m1 = list_entry(p, struct mon_bus, bus_link);
m1->u_bus->monitored = 1;
}
} else {
mbus->u_bus->monitored = 1;
}
}
mbus->nreaders++;
list_add_tail(&r->r_link, &mbus->r_list);
spin_unlock_irqrestore(&mbus->lock, flags);
kref_get(&mbus->ref);
}
/*
* Unlink reader from the bus.
*
* This is called with mon_lock taken, so we can decrement mbus->ref.
*/
void mon_reader_del(struct mon_bus *mbus, struct mon_reader *r)
{
unsigned long flags;
spin_lock_irqsave(&mbus->lock, flags);
list_del(&r->r_link);
--mbus->nreaders;
if (mbus->nreaders == 0)
mon_stop(mbus);
spin_unlock_irqrestore(&mbus->lock, flags);
kref_put(&mbus->ref, mon_bus_drop);
}
/*
*/
static void mon_bus_submit(struct mon_bus *mbus, struct urb *urb)
{
unsigned long flags;
struct list_head *pos;
struct mon_reader *r;
spin_lock_irqsave(&mbus->lock, flags);
mbus->cnt_events++;
list_for_each (pos, &mbus->r_list) {
r = list_entry(pos, struct mon_reader, r_link);
r->rnf_submit(r->r_data, urb);
}
spin_unlock_irqrestore(&mbus->lock, flags);
return;
}
static void mon_submit(struct usb_bus *ubus, struct urb *urb)
{
struct mon_bus *mbus;
if ((mbus = ubus->mon_bus) != NULL)
mon_bus_submit(mbus, urb);
mon_bus_submit(&mon_bus0, urb);
}
/*
*/
static void mon_bus_submit_error(struct mon_bus *mbus, struct urb *urb, int error)
{
unsigned long flags;
struct list_head *pos;
struct mon_reader *r;
spin_lock_irqsave(&mbus->lock, flags);
mbus->cnt_events++;
list_for_each (pos, &mbus->r_list) {
r = list_entry(pos, struct mon_reader, r_link);
r->rnf_error(r->r_data, urb, error);
}
spin_unlock_irqrestore(&mbus->lock, flags);
return;
}
static void mon_submit_error(struct usb_bus *ubus, struct urb *urb, int error)
{
struct mon_bus *mbus;
if ((mbus = ubus->mon_bus) != NULL)
mon_bus_submit_error(mbus, urb, error);
mon_bus_submit_error(&mon_bus0, urb, error);
}
/*
*/
static void mon_bus_complete(struct mon_bus *mbus, struct urb *urb, int status)
{
unsigned long flags;
struct list_head *pos;
struct mon_reader *r;
spin_lock_irqsave(&mbus->lock, flags);
mbus->cnt_events++;
list_for_each (pos, &mbus->r_list) {
r = list_entry(pos, struct mon_reader, r_link);
r->rnf_complete(r->r_data, urb, status);
}
spin_unlock_irqrestore(&mbus->lock, flags);
}
static void mon_complete(struct usb_bus *ubus, struct urb *urb, int status)
{
struct mon_bus *mbus;
if ((mbus = ubus->mon_bus) != NULL)
mon_bus_complete(mbus, urb, status);
mon_bus_complete(&mon_bus0, urb, status);
}
/* int (*unlink_urb) (struct urb *urb, int status); */
/*
* Stop monitoring.
*/
static void mon_stop(struct mon_bus *mbus)
{
struct usb_bus *ubus;
struct list_head *p;
if (mbus == &mon_bus0) {
list_for_each (p, &mon_buses) {
mbus = list_entry(p, struct mon_bus, bus_link);
/*
* We do not change nreaders here, so rely on mon_lock.
*/
if (mbus->nreaders == 0 && (ubus = mbus->u_bus) != NULL)
ubus->monitored = 0;
}
} else {
/*
* A stop can be called for a dissolved mon_bus in case of
* a reader staying across an rmmod foo_hcd, so test ->u_bus.
*/
if (mon_bus0.nreaders == 0 && (ubus = mbus->u_bus) != NULL) {
ubus->monitored = 0;
mb();
}
}
}
/*
* Add a USB bus (usually by a modprobe foo-hcd)
*
* This does not return an error code because the core cannot care less
* if monitoring is not established.
*/
static void mon_bus_add(struct usb_bus *ubus)
{
mon_bus_init(ubus);
mutex_lock(&mon_lock);
if (mon_bus0.nreaders != 0)
ubus->monitored = 1;
mutex_unlock(&mon_lock);
}
/*
* Remove a USB bus (either from rmmod foo-hcd or from a hot-remove event).
*/
static void mon_bus_remove(struct usb_bus *ubus)
{
struct mon_bus *mbus = ubus->mon_bus;
mutex_lock(&mon_lock);
list_del(&mbus->bus_link);
if (mbus->text_inited)
mon_text_del(mbus);
if (mbus->bin_inited)
mon_bin_del(mbus);
mon_dissolve(mbus, ubus);
kref_put(&mbus->ref, mon_bus_drop);
mutex_unlock(&mon_lock);
}
static int mon_notify(struct notifier_block *self, unsigned long action,
void *dev)
{
switch (action) {
case USB_BUS_ADD:
mon_bus_add(dev);
break;
case USB_BUS_REMOVE:
mon_bus_remove(dev);
}
return NOTIFY_OK;
}
static struct notifier_block mon_nb = {
.notifier_call = mon_notify,
};
/*
* Ops
*/
static struct usb_mon_operations mon_ops_0 = {
.urb_submit = mon_submit,
.urb_submit_error = mon_submit_error,
.urb_complete = mon_complete,
};
/*
* Tear usb_bus and mon_bus apart.
*/
static void mon_dissolve(struct mon_bus *mbus, struct usb_bus *ubus)
{
if (ubus->monitored) {
ubus->monitored = 0;
mb();
}
ubus->mon_bus = NULL;
mbus->u_bus = NULL;
mb();
/* We want synchronize_irq() here, but that needs an argument. */
}
/*
*/
static void mon_bus_drop(struct kref *r)
{
struct mon_bus *mbus = container_of(r, struct mon_bus, ref);
kfree(mbus);
}
/*
* Initialize a bus for us:
* - allocate mon_bus
* - refcount USB bus struct
* - link
*/
static void mon_bus_init(struct usb_bus *ubus)
{
struct mon_bus *mbus;
if ((mbus = kzalloc(sizeof(struct mon_bus), GFP_KERNEL)) == NULL)
goto err_alloc;
kref_init(&mbus->ref);
spin_lock_init(&mbus->lock);
INIT_LIST_HEAD(&mbus->r_list);
/*
* We don't need to take a reference to ubus, because we receive
* a notification if the bus is about to be removed.
*/
mbus->u_bus = ubus;
ubus->mon_bus = mbus;
mbus->text_inited = mon_text_add(mbus, ubus);
mbus->bin_inited = mon_bin_add(mbus, ubus);
mutex_lock(&mon_lock);
list_add_tail(&mbus->bus_link, &mon_buses);
mutex_unlock(&mon_lock);
return;
err_alloc:
return;
}
static void mon_bus0_init(void)
{
struct mon_bus *mbus = &mon_bus0;
kref_init(&mbus->ref);
spin_lock_init(&mbus->lock);
INIT_LIST_HEAD(&mbus->r_list);
mbus->text_inited = mon_text_add(mbus, NULL);
mbus->bin_inited = mon_bin_add(mbus, NULL);
}
/*
* Search a USB bus by number. Notice that USB bus numbers start from one,
* which we may later use to identify "all" with zero.
*
* This function must be called with mon_lock held.
*
* This is obviously inefficient and may be revised in the future.
*/
struct mon_bus *mon_bus_lookup(unsigned int num)
{
struct list_head *p;
struct mon_bus *mbus;
if (num == 0) {
return &mon_bus0;
}
list_for_each (p, &mon_buses) {
mbus = list_entry(p, struct mon_bus, bus_link);
if (mbus->u_bus->busnum == num) {
return mbus;
}
}
return NULL;
}
static int __init mon_init(void)
{
struct usb_bus *ubus;
int rc;
if ((rc = mon_text_init()) != 0)
goto err_text;
if ((rc = mon_bin_init()) != 0)
goto err_bin;
mon_bus0_init();
if (usb_mon_register(&mon_ops_0) != 0) {
printk(KERN_NOTICE TAG ": unable to register with the core\n");
rc = -ENODEV;
goto err_reg;
}
// MOD_INC_USE_COUNT(which_module?);
mutex_lock(&usb_bus_list_lock);
list_for_each_entry (ubus, &usb_bus_list, bus_list) {
mon_bus_init(ubus);
}
usb_register_notify(&mon_nb);
mutex_unlock(&usb_bus_list_lock);
return 0;
err_reg:
mon_bin_exit();
err_bin:
mon_text_exit();
err_text:
return rc;
}
static void __exit mon_exit(void)
{
struct mon_bus *mbus;
struct list_head *p;
usb_unregister_notify(&mon_nb);
usb_mon_deregister();
mutex_lock(&mon_lock);
while (!list_empty(&mon_buses)) {
p = mon_buses.next;
mbus = list_entry(p, struct mon_bus, bus_link);
list_del(p);
if (mbus->text_inited)
mon_text_del(mbus);
if (mbus->bin_inited)
mon_bin_del(mbus);
/*
* This never happens, because the open/close paths in
* file level maintain module use counters and so rmmod fails
* before reaching here. However, better be safe...
*/
if (mbus->nreaders) {
printk(KERN_ERR TAG
": Outstanding opens (%d) on usb%d, leaking...\n",
mbus->nreaders, mbus->u_bus->busnum);
atomic_set(&mbus->ref.refcount, 2); /* Force leak */
}
mon_dissolve(mbus, mbus->u_bus);
kref_put(&mbus->ref, mon_bus_drop);
}
mbus = &mon_bus0;
if (mbus->text_inited)
mon_text_del(mbus);
if (mbus->bin_inited)
mon_bin_del(mbus);
mutex_unlock(&mon_lock);
mon_text_exit();
mon_bin_exit();
}
module_init(mon_init);
module_exit(mon_exit);
MODULE_LICENSE("GPL");