linux-kernel - Re: BUG: KASAN: use-after-free in usb_hcd_unlink

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Date:   Mon, 23 Mar 2020 07:39:09 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Kyungtae Kim <kt0755@...il.com>
Cc:     laurentiu.tudor@....com, noring@...rew.org,
        chunfeng.yun@...iatek.com, felipe.balbi@...ux.intel.com,
        tweek@...gle.com, tony@...mide.com, rrangel@...omium.org,
        m.szyprowski@...sung.com, Dave Tian <dave.jing.tian@...il.com>,
        linux-usb@...r.kernel.og, syzkaller <syzkaller@...glegroups.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: BUG: KASAN: use-after-free in usb_hcd_unlink_urb+0x5f/0x170
 drivers/usb/core/hcd.c

On Mon, Mar 23, 2020 at 02:16:43AM -0400, Kyungtae Kim wrote:
> We report a bug (in linux-5.5.11) found by FuzzUSB (a modified version
> of syzkaller)
> 
> In function usb_hcd_unlink_urb (driver/usb/core/hcd.c:1607), it tries to
> read "urb->use_count". But it seems the instance "urb" was
> already freed (right after urb->dev at line 1597) by the function "urb_destroy"
> in a different thread, which caused memory access violation.
> To solve, it may need to check if urb is valid before urb->use_count,
> to avoid such freed memory access.

Can you send a patch for this?  Do you have a reproducer?

thanks,

greg k-h