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USB: Proper handling of Race Condition when two USB class drivers try to call init_usb_class simultaneously
There is race condition when two USB class drivers try to call init_usb_class at the same time and leads to crash. code path: probe->usb_register_dev->init_usb_class To solve this, mutex locking has been added in init_usb_class() and destroy_usb_class(). As pointed by Alan, removed "if (usb_class)" test from destroy_usb_class() because usb_class can never be NULL there. Signed-off-by: Ajay Kaher <ajay.kaher@samsung.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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parent
041370cce8
commit
2f86a96be0
1 changed files with 7 additions and 2 deletions
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@ -29,6 +29,7 @@
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#define MAX_USB_MINORS 256
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static const struct file_operations *usb_minors[MAX_USB_MINORS];
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static DECLARE_RWSEM(minor_rwsem);
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static DEFINE_MUTEX(init_usb_class_mutex);
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static int usb_open(struct inode *inode, struct file *file)
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{
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@ -111,8 +112,9 @@ static void release_usb_class(struct kref *kref)
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static void destroy_usb_class(void)
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{
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if (usb_class)
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kref_put(&usb_class->kref, release_usb_class);
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mutex_lock(&init_usb_class_mutex);
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kref_put(&usb_class->kref, release_usb_class);
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mutex_unlock(&init_usb_class_mutex);
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}
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int usb_major_init(void)
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@ -173,7 +175,10 @@ int usb_register_dev(struct usb_interface *intf,
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if (intf->minor >= 0)
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return -EADDRINUSE;
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mutex_lock(&init_usb_class_mutex);
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retval = init_usb_class();
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mutex_unlock(&init_usb_class_mutex);
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if (retval)
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return retval;
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