diff options
| author | Ajay Kaher <ajay.kaher@samsung.com> | 2017-03-28 08:09:32 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-05-20 14:26:58 +0200 |
| commit | de9d2d297ebe4d591efd41902c568e3ef4774c43 (patch) | |
| tree | 34abcd18dcb21fbd5485204ce69c17184dc0a3df | |
| parent | fcd9a083cd2283574c46b78f39f0d7a83c3cc7d6 (diff) | |
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/usb/core/file.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/drivers/usb/core/file.c b/drivers/usb/core/file.c index ea337a718cc1..b3de806085f0 100644 --- a/drivers/usb/core/file.c +++ b/drivers/usb/core/file.c @@ -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; |