| From 2f86a96be0ccb1302b7eee7855dbee5ce4dc5dfb Mon Sep 17 00:00:00 2001 |
| From: Ajay Kaher <ajay.kaher@samsung.com> |
| Date: Tue, 28 Mar 2017 08:09:32 -0400 |
| Subject: [PATCH] USB: Proper handling of Race Condition when two USB class |
| drivers try to call init_usb_class simultaneously |
| |
| commit 2f86a96be0ccb1302b7eee7855dbee5ce4dc5dfb 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> |
| Cc: stable <stable@vger.kernel.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| diff --git a/drivers/usb/core/file.c b/drivers/usb/core/file.c |
| index e26bd5e773ad..87ad6b6bfee8 100644 |
| --- a/drivers/usb/core/file.c |
| +++ b/drivers/usb/core/file.c |
| @@ -29,6 +29,7 @@ |
| #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) |
| { |
| @@ -111,8 +112,9 @@ 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) |
| @@ -173,7 +175,10 @@ 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; |
| |
| -- |
| 2.12.0 |
| |