linux-kernel - Re: [PATCH -resend 5/6] acpi: ec_sys: access user space with get_user()/put

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Date:	Thu, 23 May 2013 01:39 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	jirislaby@...il.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, Vasiliy Kulikov <segooon@...il.com>,
	Thomas Renninger <trenn@...e.de>, Len Brown <lenb@...nel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH -resend 5/6] acpi: ec_sys: access user space with get_user()/put_user()

On Wednesday, May 22, 2013 02:59:11 PM Jiri Slaby wrote:
> From: Vasiliy Kulikov <segooon@...il.com>
> 
> User space pointer may not be dereferenced. Use get_user()/put_user()
> instead and check their return codes.
> 
> Signed-off-by: Vasiliy Kulikov <segooon@...il.com>
> Signed-off-by: Thomas Renninger <trenn@...e.de>
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> Cc: Len Brown <lenb@...nel.org>
> Cc: "Rafael J. Wysocki" <rjw@...k.pl>
> Cc: linux-acpi@...r.kernel.org

Interesting.  It looks like it actually didn't reach linux-acpi.

Anyway, I'm going to queue it up for v3.11.

Thanks,
Rafael


> ---
>  drivers/acpi/ec_sys.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/acpi/ec_sys.c b/drivers/acpi/ec_sys.c
> index 7586544..4e7b798 100644
> --- a/drivers/acpi/ec_sys.c
> +++ b/drivers/acpi/ec_sys.c
> @@ -12,6 +12,7 @@
>  #include <linux/acpi.h>
>  #include <linux/debugfs.h>
>  #include <linux/module.h>
> +#include <linux/uaccess.h>
>  #include "internal.h"
>  
>  MODULE_AUTHOR("Thomas Renninger <trenn@...e.de>");
> @@ -34,7 +35,6 @@ static ssize_t acpi_ec_read_io(struct file *f, char __user *buf,
>  	 * struct acpi_ec *ec = ((struct seq_file *)f->private_data)->private;
>  	 */
>  	unsigned int size = EC_SPACE_SIZE;
> -	u8 *data = (u8 *) buf;
>  	loff_t init_off = *off;
>  	int err = 0;
>  
> @@ -47,9 +47,15 @@ static ssize_t acpi_ec_read_io(struct file *f, char __user *buf,
>  		size = count;
>  
>  	while (size) {
> -		err = ec_read(*off, &data[*off - init_off]);
> +		u8 byte_read;
> +		err = ec_read(*off, &byte_read);
>  		if (err)
>  			return err;
> +		if (put_user(byte_read, buf + *off - init_off)) {
> +			if (*off - init_off)
> +				return *off - init_off; /* partial read */
> +			return -EFAULT;
> +		}
>  		*off += 1;
>  		size--;
>  	}
> @@ -65,7 +71,6 @@ static ssize_t acpi_ec_write_io(struct file *f, const char __user *buf,
>  
>  	unsigned int size = count;
>  	loff_t init_off = *off;
> -	u8 *data = (u8 *) buf;
>  	int err = 0;
>  
>  	if (*off >= EC_SPACE_SIZE)
> @@ -76,7 +81,12 @@ static ssize_t acpi_ec_write_io(struct file *f, const char __user *buf,
>  	}
>  
>  	while (size) {
> -		u8 byte_write = data[*off - init_off];
> +		u8 byte_write;
> +		if (get_user(byte_write, buf + *off - init_off)) {
> +			if (*off - init_off)
> +				return *off - init_off; /* partial write */
> +			return -EFAULT;
> +		}
>  		err = ec_write(*off, byte_write);
>  		if (err)
>  			return err;
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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