linux-kernel - Re: [BUG] usb: serial: garmin_gps: A possible concurrency use-after-free bug

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Message-ID: <20181220134609.GA27701@localhost>
Date:   Thu, 20 Dec 2018 14:46:09 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     Johan Hovold <johan@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] usb: serial: garmin_gps: A possible concurrency
 use-after-free bug

On Thu, Dec 20, 2018 at 09:41:16PM +0800, Jia-Ju Bai wrote:
> In drivers/usb/serial/garmin_gps.c,
> the functions garmin_read_bulk_callback() and garmin_write_bulk_callback()
> may be concurrently executed.
> 
> In garmin_write_bulk_callback() on line 969:
>      kfree(urb->transfer_buffer);
> In garmin_read_bulk_callback() on line 1165:
>      unsigned char *data = urb->transfer_buffer;
> Thus, a concurrency use-after-free bug may occur.

No, they operate on different struct urb.

> This possible bug is found by a static analysis tool written by myself.

Seems you need to update your tool. Please also make sure to review its
output before reporting anything.

Thanks,
Johan