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authorAlan Stern <stern@rowland.harvard.edu>2007-05-22 11:46:41 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2007-07-12 16:29:48 -0700
commitd4ead16f50f9ad30bdc7276ec8fee7a24c72f294 (patch)
treee1905abbc393cc4d73180dd7b9e1cf860378b590 /drivers/usb/misc/iowarrior.c
parent55e5fdfa541ec7bf1b1613624ed4dd8cdacaa841 (diff)
USB: prevent char device open/deregister race
This patch (as908) adds central protection in usbcore for the prototypical race between opening and unregistering a char device. The spinlock used to protect the minor-numbers array is replaced with an rwsem, which can remain locked across a call to a driver's open() method. This guarantees that open() and deregister() will be mutually exclusive. The private locks currently used in several individual drivers for this purpose are no longer necessary, and the patch removes them. The following USB drivers are affected: usblcd, idmouse, auerswald, legousbtower, sisusbvga/sisusb, ldusb, adutux, iowarrior, and usb-skeleton. As a side effect of this change, usb_deregister_dev() must not be called while holding a lock that is acquired by open(). Unfortunately a number of drivers do this, but luckily the solution is simple: call usb_deregister_dev() before acquiring the lock. In addition to these changes (and their consequent code simplifications), the patch fixes a use-after-free bug in adutux and a race between open() and release() in iowarrior. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/usb/misc/iowarrior.c')
-rw-r--r--drivers/usb/misc/iowarrior.c26
1 files changed, 8 insertions, 18 deletions
diff --git a/drivers/usb/misc/iowarrior.c b/drivers/usb/misc/iowarrior.c
index 3bb33f7bfa36..28548d186712 100644
--- a/drivers/usb/misc/iowarrior.c
+++ b/drivers/usb/misc/iowarrior.c
@@ -100,8 +100,6 @@ struct iowarrior {
/*--------------*/
/* globals */
/*--------------*/
-/* prevent races between open() and disconnect() */
-static DECLARE_MUTEX(disconnect_sem);
/*
* USB spec identifies 5 second timeouts.
@@ -600,22 +598,18 @@ static int iowarrior_open(struct inode *inode, struct file *file)
subminor = iminor(inode);
- /* prevent disconnects */
- down(&disconnect_sem);
-
interface = usb_find_interface(&iowarrior_driver, subminor);
if (!interface) {
err("%s - error, can't find device for minor %d", __FUNCTION__,
subminor);
- retval = -ENODEV;
- goto out;
+ return -ENODEV;
}
dev = usb_get_intfdata(interface);
- if (!dev) {
- retval = -ENODEV;
- goto out;
- }
+ if (!dev)
+ return -ENODEV;
+
+ mutex_lock(&dev->mutex);
/* Only one process can open each device, no sharing. */
if (dev->opened) {
@@ -636,7 +630,7 @@ static int iowarrior_open(struct inode *inode, struct file *file)
retval = 0;
out:
- up(&disconnect_sem);
+ mutex_unlock(&dev->mutex);
return retval;
}
@@ -868,19 +862,16 @@ static void iowarrior_disconnect(struct usb_interface *interface)
struct iowarrior *dev;
int minor;
- /* prevent races with open() */
- down(&disconnect_sem);
-
dev = usb_get_intfdata(interface);
usb_set_intfdata(interface, NULL);
- mutex_lock(&dev->mutex);
-
minor = dev->minor;
/* give back our minor */
usb_deregister_dev(interface, &iowarrior_class);
+ mutex_lock(&dev->mutex);
+
/* prevent device read, write and ioctl */
dev->present = 0;
@@ -898,7 +889,6 @@ static void iowarrior_disconnect(struct usb_interface *interface)
/* no process is using the device, cleanup now */
iowarrior_delete(dev);
}
- up(&disconnect_sem);
dev_info(&interface->dev, "I/O-Warror #%d now disconnected\n",
minor - IOWARRIOR_MINOR_BASE);