netdev - Re: [PATCH] net/tun: fix ioctl() based info leaks

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Date:	Mon, 30 Jul 2012 01:11:28 +0200
From:	richard -rw- weinberger <richard.weinberger@...il.com>
To:	Mathias Krause <minipli@...glemail.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] net/tun: fix ioctl() based info leaks

On Sun, Jul 29, 2012 at 10:58 PM, Mathias Krause <minipli@...glemail.com> wrote:
> The tun module leaks up to 36 bytes of memory by not initializing a
> structure located on the stack that gets copied to user memory by the
> TUNGETIFF and SIOCGIFHWADDR ioctl()s.
>
> Signed-off-by: Mathias Krause <minipli@...glemail.com>
> ---
>  drivers/net/tun.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 987aeef..cadeb94 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1252,9 +1252,12 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
>         int vnet_hdr_sz;
>         int ret;
>
> -       if (cmd == TUNSETIFF || _IOC_TYPE(cmd) == 0x89)
> +       if (cmd == TUNSETIFF || _IOC_TYPE(cmd) == 0x89) {
>                 if (copy_from_user(&ifr, argp, ifreq_len))
>                         return -EFAULT;
> +       } else {
> +               memset(&ifr, 0, sizeof(ifr));
> +       }
>
>         if (cmd == TUNGETFEATURES) {
>                 /* Currently this just means: "what IFF flags are valid?".

The fix makes sense to me.

Beside of the fix, why are you adding braces to if and else?
We don't use braces on single statements.

-- 
Thanks,
//richard
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