linux-kernel - Re: [PATCH] samples: Fix `echo 1 > /proc/int-fifo` never return error

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Message-ID: <1423045101.8226.5.camel@seibold.net>
Date:	Wed, 04 Feb 2015 11:18:21 +0100
From:	Stefani Seibold <stefani@...bold.net>
To:	Wang Long <long.wanglong@...wei.com>
Cc:	peifeiyue@...wei.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] samples: Fix `echo 1 > /proc/int-fifo` never return
 error

The example is intended for int types, not for strings. So it is not a
bug, it's a feature ;-) But anyway, if you prefer to handle with strings
your are okay by me.

Am Dienstag, den 03.02.2015, 11:51 +0000 schrieb Wang Long:
> echo 99 > /proc/int-fifo       ------------> Never return
> echo 1000 > /proc/int-fifo     ------------> Never return
> 
> this patch fix it.
> 
> Signed-off-by: Wang Long <long.wanglong@...wei.com>
> ---
>  samples/kfifo/inttype-example.c | 51 ++++++++++++++++++++++++++++++++---------
>  1 file changed, 40 insertions(+), 11 deletions(-)
> 
> diff --git a/samples/kfifo/inttype-example.c b/samples/kfifo/inttype-example.c
> index 8dc3c2e..cc0db5f 100644
> --- a/samples/kfifo/inttype-example.c
> +++ b/samples/kfifo/inttype-example.c
> @@ -6,6 +6,7 @@
>   * Released under the GPL version 2 only.
>   *
>   */
> +#include <asm/uaccess.h>
>  
>  #include <linux/init.h>
>  #include <linux/module.h>
> @@ -23,6 +24,9 @@
>  /* name of the proc entry */
>  #define	PROC_FIFO	"int-fifo"
>  
> +/* Worst case buffer size needed for holding an integer. */
> +#define PROC_NUMBUF 13
> +
>  /* lock for procfs read access */
>  static DEFINE_MUTEX(read_lock);
>  
> @@ -108,33 +112,58 @@ static int __init testfunc(void)
>  static ssize_t fifo_write(struct file *file, const char __user *buf,
>  						size_t count, loff_t *ppos)
>  {
> -	int ret;
> -	unsigned int copied;
> +	char buffer[PROC_NUMBUF];
> +	int value;
> +	int err;
>  
> -	if (mutex_lock_interruptible(&write_lock))
> -		return -ERESTARTSYS;
> +	memset(buffer, 0, sizeof(buffer));
>  
> -	ret = kfifo_from_user(&test, buf, count, &copied);
> +	if (count > sizeof(buffer) - 1)
> +		count = sizeof(buffer) - 1;
> +	if (copy_from_user(buffer, buf, count)) {
> +		err = -EFAULT;
> +		goto out;
> +	}
>  
> -	mutex_unlock(&write_lock);
> +	err = kstrtoint(strstrip(buffer), 0, &value);
> +	if (err)
> +		goto out;
> +
> +	if (kfifo_is_full(&test)) {
> +		err = -EINVAL;
> +		goto out;
> +	}
>  
> -	return ret ? ret : copied;
> +	if (mutex_lock_interruptible(&write_lock))
> +		return -ERESTARTSYS;
> +	kfifo_put(&test, value);
> +	mutex_unlock(&write_lock);
> +out:
> +	return err < 0 ? err : count;
>  }
>  
>  static ssize_t fifo_read(struct file *file, char __user *buf,
>  						size_t count, loff_t *ppos)
>  {
> -	int ret;
> -	unsigned int copied;
> +	char buffer[PROC_NUMBUF * FIFO_SIZE];
> +	int value;
> +	size_t	len = 0;
> +	ssize_t	ret = -1;
> +
> +	memset(buffer, 0, sizeof(buffer));
>  
>  	if (mutex_lock_interruptible(&read_lock))
>  		return -ERESTARTSYS;
>  
> -	ret = kfifo_to_user(&test, buf, count, &copied);
> +	while (!kfifo_is_empty(&test)){
> +		ret = kfifo_get(&test, &value);
> +		len = snprintf(buffer, sizeof(buffer), "%s%d\n", buffer, value);
> +	}
>  
>  	mutex_unlock(&read_lock);
> +	ret = copy_to_user(buf, buffer, len);
>  
> -	return ret ? ret : copied;
> +	return ret ? ret : len;
>  }
>  
>  static const struct file_operations fifo_fops = {


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