linux-kernel - Re: [PATCH] char: ppdev: check if ioctl argument is present and valid

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAK8P3a1cSCDAHDNFX9KrqQ3-7TNsidzyX6_Yn-fmVOQGqyCHCA@mail.gmail.com>
Date:   Thu, 8 Oct 2020 21:35:32 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Harshal Chaudhari <harshalchau04@...il.com>
Cc:     gregkh <gregkh@...uxfoundation.org>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] char: ppdev: check if ioctl argument is present and valid

On Thu, Oct 8, 2020 at 8:27 PM Harshal Chaudhari
<harshalchau04@...il.com> wrote:
>
> Checking the argument passed to the ioctl is valid
> or not. if not then return -EINVAL.
>
> Signed-off-by: Harshal Chaudhari <harshalchau04@...il.com>
> ---
>  drivers/char/ppdev.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/ppdev.c b/drivers/char/ppdev.c
> index 38b46c7d1737..001392980202 100644
> --- a/drivers/char/ppdev.c
> +++ b/drivers/char/ppdev.c
> @@ -354,7 +354,7 @@ static int pp_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>         unsigned int minor = iminor(file_inode(file));
>         struct pp_struct *pp = file->private_data;
>         struct parport *port;
> -       void __user *argp = (void __user *)arg;
> +       void __user *argp = NULL;
>         struct ieee1284_info *info;
>         unsigned char reg;
>         unsigned char mask;

Assigning to NULL serves no purpose here.

> @@ -364,6 +364,16 @@ static int pp_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>         struct timespec64 ts;
>         int ret;
>
> +       if (_IOC_TYPE(cmd) != PP_IOCTL)
> +               return -ENOTTY;

This looks correct but is normally done as a "default" case

> +       /* check if ioctl argument is present and valid */
> +       if (_IOC_DIR(cmd) != _IOC_NONE) {
> +               argp = (void __user *)arg;
> +               if (!argp)
> +                       return -EINVAL;
> +       }

This is a change in behavior, it changes the return code from the correct
-EFAULT to an unusual -EINVAL for the special case that the pointer
is NULL compared to other invalid pointers.

      Arnd