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USB: Proper handling of Race Condition when two USB class drivers try to call init_usb_class simultaneously

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commit 2f86a96be0 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ajay Kaher
2017-03-28 08:09:32 -04:00
committed by Greg Kroah-Hartman
parent fcd9a083cd
commit de9d2d297e
1 changed files with 7 additions and 2 deletions
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9
drivers/usb/core/file.c
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@@ -26,6 +26,7 @@
#define MAX_USB_MINORS 256
static const struct file_operations *usb_minors[MAX_USB_MINORS];
static DECLARE_RWSEM(minor_rwsem);
static DEFINE_MUTEX(init_usb_class_mutex);
static int usb_open(struct inode *inode, struct file *file)
{
@@ -108,8 +109,9 @@ static void release_usb_class(struct kref *kref)
static void destroy_usb_class(void)
{
if (usb_class)
kref_put(&usb_class->kref, release_usb_class);
mutex_lock(&init_usb_class_mutex);
kref_put(&usb_class->kref, release_usb_class);
mutex_unlock(&init_usb_class_mutex);
}
int usb_major_init(void)
@@ -171,7 +173,10 @@ int usb_register_dev(struct usb_interface *intf,
if (intf->minor >= 0)
return -EADDRINUSE;
mutex_lock(&init_usb_class_mutex);
retval = init_usb_class();
mutex_unlock(&init_usb_class_mutex);
if (retval)
return retval;