linux-kernel - Re: [PATCH] remoteproc: Fix potential race condition in rproc

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Date:	Tue, 14 Jun 2016 11:34:01 -0700
From:	Bjorn Andersson <bjorn.andersson@...aro.org>
To:	Dave Gerlach <d-gerlach@...com>
Cc:	linux-kernel@...r.kernel.org, linux-remoteproc@...r.kernel.org,
	Ohad Ben-Cohen <ohad@...ery.com>, Suman Anna <s-anna@...com>
Subject: Re: [PATCH] remoteproc: Fix potential race condition in rproc_add

On Wed 25 May 13:41 PDT 2016, Dave Gerlach wrote:

> rproc_add adds the newly created remoteproc to a list for use by
> rproc_get_by_phandle and then does some additional processing to finish
> adding the remoteproc. This leaves a small window of time in which the
> rproc is available in the list but not yet fully initialized, so if
> another driver comes along and gets a handle to the rproc, it will be
> invalid. Rearrange the code in rproc_add to make sure the rproc is added
> to the list only after it has been successfuly initialized.
> 
> Fixes: fec47d863587 ("remoteproc: introduce rproc_get_by_phandle API")
> Signed-off-by: Dave Gerlach <d-gerlach@...com>

Applied and added Cc: stable.

Regards,
Bjorn

> ---
>  drivers/remoteproc/remoteproc_core.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index db3958b3f094..fe0539ed9cb5 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -1264,11 +1264,6 @@ int rproc_add(struct rproc *rproc)
>  	if (ret < 0)
>  		return ret;
>  
> -	/* expose to rproc_get_by_phandle users */
> -	mutex_lock(&rproc_list_mutex);
> -	list_add(&rproc->node, &rproc_list);
> -	mutex_unlock(&rproc_list_mutex);
> -
>  	dev_info(dev, "%s is available\n", rproc->name);
>  
>  	dev_info(dev, "Note: remoteproc is still under development and considered experimental.\n");
> @@ -1276,8 +1271,16 @@ int rproc_add(struct rproc *rproc)
>  
>  	/* create debugfs entries */
>  	rproc_create_debug_dir(rproc);
> +	ret = rproc_add_virtio_devices(rproc);
> +	if (ret < 0)
> +		return ret;
>  
> -	return rproc_add_virtio_devices(rproc);
> +	/* expose to rproc_get_by_phandle users */
> +	mutex_lock(&rproc_list_mutex);
> +	list_add(&rproc->node, &rproc_list);
> +	mutex_unlock(&rproc_list_mutex);
> +
> +	return 0;
>  }
>  EXPORT_SYMBOL(rproc_add);
>