linux-kernel - Re: [PATCH] Set bounds on what /proc/self/make-it-fail accepts.

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Message-ID: <alpine.DEB.2.02.1402181429060.20772@chino.kir.corp.google.com>
Date:	Tue, 18 Feb 2014 14:32:02 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Dave Jones <davej@...hat.com>,
	Akinobu Mita <akinobu.mita@...il.com>
cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH] Set bounds on what /proc/self/make-it-fail accepts.

On Tue, 18 Feb 2014, Dave Jones wrote:

> /proc/self/make-it-fail is a boolean, but accepts any number, including
> negative ones. Change variable to unsigned, and cap upper bound at 1.
> 
> Signed-off-by: Dave Jones <davej@...oraproject.org>
> 

Hmm, this would break anything that uses anything other than one to enable 
it, but it looks like Documentation/fault-injection/fault-injection.txt 
only provides an example for when it does equal one, so it's probably an 
ok change.  I'm just wondering why non-zero is wrong?  Is this an 
interface that will be extended to support other modes?

Adding Akinobu to the cc.

> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 51507065263b..b926377c354f 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -1207,7 +1207,7 @@ static ssize_t proc_fault_inject_read(struct file * file, char __user * buf,
>  	struct task_struct *task = get_proc_task(file_inode(file));
>  	char buffer[PROC_NUMBUF];
>  	size_t len;
> -	int make_it_fail;
> +	unsigned int make_it_fail;
>  
>  	if (!task)
>  		return -ESRCH;
> @@ -1224,7 +1224,7 @@ static ssize_t proc_fault_inject_write(struct file * file,
>  {
>  	struct task_struct *task;
>  	char buffer[PROC_NUMBUF], *end;
> -	int make_it_fail;
> +	unsigned int make_it_fail;
>  
>  	if (!capable(CAP_SYS_RESOURCE))
>  		return -EPERM;
> @@ -1236,6 +1236,9 @@ static ssize_t proc_fault_inject_write(struct file * file,
>  	make_it_fail = simple_strtol(strstrip(buffer), &end, 0);
>  	if (*end)
>  		return -EINVAL;
> +	if (make_it_fail > 1)
> +		return -EINVAL;
> +
>  	task = get_proc_task(file_inode(file));
>  	if (!task)
>  		return -ESRCH;
--
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