On Fri, Mar 17, 2017 at 10:56:37AM +0000, Ajay Kaher wrote:
> 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.ka...@samsung.com>
> Acked-by: Alan Stern <st...@rowland.harvard.edu>
> ---
> drivers/usb/core/file.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/core/file.c b/drivers/usb/core/file.c
> index 822ced9..422ce7b 100644
> --- a/drivers/usb/core/file.c
> +++ b/drivers/usb/core/file.c
> @@ -27,6 +27,7 @@
> #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)
> {
> @@ -109,8 +110,9 @@ 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;
>
I get the following errors when trying to apply this patch:
Applying: USB: Proper handling of Race Condition when two USB class drivers try
to call init_usb_class simultaneously
.git/rebase-apply/patch:13: trailing whitespace.
static DEFINE_MUTEX(init_usb_class_mutex);
.git/rebase-apply/patch:23: trailing whitespace.
mutex_lock(&init_usb_class_mutex);
.git/rebase-apply/patch:24: trailing whitespace.
kref_put(&usb_class->kref, release_usb_class);
.git/rebase-apply/patch:25: trailing whitespace.
mutex_unlock(&init_usb_class_mutex);
.git/rebase-apply/patch:33: trailing whitespace.
mutex_lock(&init_usb_class_mutex);
error: patch failed: drivers/usb/core/file.c:27
error: drivers/usb/core/file.c: patch does not apply
Patch failed at 0001 USB: Proper handling of Race Condition when two USB class
drivers try to call init_usb_class simultaneously
Are you sure you made this in the correct format? Seems that the patch
has dos line-ends :(
Please fix up and resend.
thanks,
greg k-h
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