linux-kernel - Re: [PATCH] w1: do not unlock unheld list_mutex in __w1_remove_master

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Date:	Thu, 01 May 2014 00:45:18 +0400
From:	Alexey Khoroshilov <khoroshilov@...ras.ru>
To:	David Fries <David@...es.net>, Evgeniy Polyakov <zbr@...emap.net>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, ldv-project@...uxtesting.org
Subject: Re: [PATCH] w1: do not unlock unheld list_mutex in __w1_remove_master_device()

As far as it is 3.15-rc1 regression introduced by 9fcbbac5ded48,
it makes sense to fix it in 3.15 cycle.

--
Alexey

On 01.05.2014 00:37, Alexey Khoroshilov wrote:
> w1_process_callbacks() expects to be called with dev->list_mutex held,
> but it is the fact only in w1_process(). __w1_remove_master_device()
> calls w1_process_callbacks() after it releases list_mutex.
>
> The patch fixes __w1_remove_master_device() to acquire list_mutex
> for w1_process_callbacks(). It is implemented by moving
> w1_process_callbacks() functionality to __w1_process_callbacks()
> and adding a wrapper with the old name.
>
> Found by Linux Driver Verification project (linuxtesting.org).
>
> Signed-off-by: Alexey Khoroshilov <khoroshilov@...ras.ru>
> ---
>  drivers/w1/w1.c |  8 +++++---
>  drivers/w1/w1.h | 13 ++++++++++++-
>  2 files changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
> index ff52618cafbe..e507c51512aa 100644
> --- a/drivers/w1/w1.c
> +++ b/drivers/w1/w1.c
> @@ -1075,12 +1075,14 @@ static void w1_search_process(struct w1_master *dev, u8 search_type)
>  }
>  
>  /**
> - * w1_process_callbacks() - execute each dev->async_list callback entry
> + * __w1_process_callbacks() - execute each dev->async_list callback entry
>   * @dev: w1_master device
>   *
> + * The w1 master list_mutex must be held.
> + *
>   * Return: 1 if there were commands to executed 0 otherwise
>   */
> -int w1_process_callbacks(struct w1_master *dev)
> +int __w1_process_callbacks(struct w1_master *dev)
>  {
>  	int ret = 0;
>  	struct w1_async_cmd *async_cmd, *async_n;
> @@ -1122,7 +1124,7 @@ int w1_process(void *data)
>  		/* Note, w1_process_callback drops the lock while processing,
>  		 * but locks it again before returning.
>  		 */
> -		if (!w1_process_callbacks(dev) && jremain) {
> +		if (!__w1_process_callbacks(dev) && jremain) {
>  			/* a wake up is either to stop the thread, process
>  			 * callbacks, or search, it isn't process callbacks, so
>  			 * schedule a search.
> diff --git a/drivers/w1/w1.h b/drivers/w1/w1.h
> index 734dab7fc687..e357321a5e13 100644
> --- a/drivers/w1/w1.h
> +++ b/drivers/w1/w1.h
> @@ -341,9 +341,20 @@ extern int w1_max_slave_ttl;
>  extern struct list_head w1_masters;
>  extern struct mutex w1_mlock;
>  
> -extern int w1_process_callbacks(struct w1_master *dev);
> +extern int __w1_process_callbacks(struct w1_master *dev);
>  extern int w1_process(void *);
>  
> +static inline int w1_process_callbacks(struct w1_master *dev)
> +{
> +	int ret;
> +
> +	mutex_lock(&dev->list_mutex);
> +	ret = __w1_process_callbacks(dev);
> +	mutex_unlock(&dev->list_mutex);
> +	return ret;
> +}
> +
> +
>  #endif /* __KERNEL__ */
>  
>  #endif /* __W1_H */

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