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authorAjay Kaher <ajay.kaher@samsung.com>2017-03-28 08:09:32 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-03-29 11:55:25 +0200
commit2f86a96be0ccb1302b7eee7855dbee5ce4dc5dfb (patch)
tree5babb1236173c80b67a53cc0adb5420a87250503 /drivers/usb/core/file.c
parent041370cce889510163d9c1f677dc298d37bfb732 (diff)
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>
Diffstat (limited to 'drivers/usb/core/file.c')
-rw-r--r--drivers/usb/core/file.c9
1 files changed, 7 insertions, 2 deletions
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;