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[PATCH 4.10 08/93] USB: Proper handling of Race Condition when two USB class drivers try to call init_usb_class simultaneously

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4.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ajay Kaher <ajay.kaher@samsung.com>

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/core/file.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- 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 kre
 
 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_interfac
 	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;
 

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[PATCH 4.10 00/93] 4.10.17-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 22/93] x86/boot: Fix BSS corruption/overwrite bug in early x86 kernel startup Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 34/93] crypto: ccp - Disable interrupts early on unload Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 30/93] block: fix blk_integrity_register to use templates interval_exp if not 0 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 03/93] target/fileio: Fix zero-length READ and WRITE handling Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 54/93] orangefs: fix bounds check for listxattr Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 62/93] Fix match_prepath() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 21/93] usb: misc: legousbtower: Fix buffers on stack Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 56/93] orangefs: do not set getattr_time on orangefs_lookup Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 57/93] orangefs: do not check possibly stale size on truncate Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 02/93] target: Fix compare_and_write_callback handling for non GOOD status Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 07/93] USB: serial: ftdi_sio: add device ID for Microsemi/Arrow SF2PLUS Dev Kit Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 08/93] USB: Proper handling of Race Condition when two USB class drivers try to call init_usb_class simultaneously Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 59/93] ceph: fix memory leak in __ceph_setxattr() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 43/93] IB/core: Fix sysfs registration error flow Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 26/93] perf/x86: Fix Broadwell-EP DRAM RAPL events Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 44/93] IB/core: For multicast functions, verify that LIDs are multicast LIDs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 13:50 +0200
  [PATCH 4.10 11/93] staging: vt6656: use off stack for out buffer USB transfers. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 14:00 +0200
  [PATCH 4.10 18/93] usb: Make sure usb/phy/of gets built-in Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 14:00 +0200
  [PATCH 4.10 01/93] xen: adjust early dom0 p2m handling to xen hypervisor behavior Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 14:00 +0200
  [PATCH 4.10 12/93] staging: gdm724x: gdm_mux: fix use-after-free on module unload Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 14:00 +0200
  [PATCH 4.10 14/93] staging: comedi: jr3_pci: fix possible null pointer dereference Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 14:00 +0200
  Re: [PATCH 4.10 00/93] 4.10.17-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-05-18 19:40 +0200
  Re: [PATCH 4.10 00/93] 4.10.17-stable review Guenter Roeck <linux@roeck-us.net> - 2017-05-19 03:20 +0200

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