linux-kernel - Possible bug in cypress

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Message-ID: <fcbc78fa-7b76-cad1-9a66-041f793df4a7@ispras.ru>
Date:   Tue, 22 Aug 2017 15:11:24 +0300
From:   Anton Volkov <avolkov@...ras.ru>
To:     dignome@...il.com, koyama@...stlight.net, johan@...nel.org
Cc:     gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, ldv-project@...uxtesting.org,
        Alexey Khoroshilov <khoroshilov@...ras.ru>
Subject: Possible bug in cypress_m8.ko

Hello.

Judging by the code of cypress_m8.c some functions are considered to be 
capable of working concurrently with other functions, e.g. cypress_open.
There are, however, entities that are protected by the locks at one 
place and not protected in another. Lines are given using the info from 
Linux kernel v4.12. Example:

cypress_send
   spin_lock_irqsave
   priv->write_urb_in_use = 1;
   spin_lock_irqrestore
   (cypress_m8.c: lines 761-763)
   ...
   if (result) {
      priv->write_urb_in_use = 0; //without lock protection
      (cypress_m8.c: line 783)
   }

Is it a bug?

Thank you for your time.

-- Anton Volkov
Linux Verification Center, ISPRAS
web: http://linuxtesting.org
e-mail: avolkov@...ras.ru