linux-kernel - Re: [PATCH] w1: keep balance of mutex locks and refcnts

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Date:   Sun, 01 Oct 2017 08:55:09 +0300
From:   Evgeniy Polyakov <zbr@...emap.net>
To:     Alexey Khoroshilov <khoroshilov@...ras.ru>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "ldv-project@...uxtesting.org" <ldv-project@...uxtesting.org>
Subject: Re: [PATCH] w1: keep balance of mutex locks and refcnts

Hi Alex

29.09.2017, 23:23, "Alexey Khoroshilov" <khoroshilov@...ras.ru>:
> w1_therm_eeprom() and w1_DS18B20_precision() decrement THERM_REFCNT
> on error paths, while they did not increment it yet.
>
> read_therm() unlocks bus mutex on some error paths,
> while it is not acquired.
>
> The patch makes sure all the functions keep the balance in usage of
> the mutex and the THERM_REFCNT.
>
> Found by Linux Driver Verification project (linuxtesting.org).

Yes, this looks like a bug, thanks for finding it!

Please update your patch to use single exit point and not a mix of returns in the body of the function.

>          ret = mutex_lock_interruptible(&dev->bus_mutex);
>          if (ret != 0)
> - goto post_unlock;
> + return ret;
>
>          if (!sl->family_data) {
> - ret = -ENODEV;
> - goto pre_unlock;
> + mutex_unlock(&dev->bus_mutex);
> + return -ENODEV;
>          }