linux-kernel - Re: [PATCH] time: settimeofday: validate the values of tv fomr user

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Message-ID: <alpine.DEB.2.11.1412021209020.3961@nanos>
Date:	Tue, 2 Dec 2014 12:16:43 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Sasha Levin <sasha.levin@...cle.com>
cc:	linux-kernel@...r.kernel.org, John Stultz <john.stultz@...aro.org>
Subject: Re: [PATCH] time: settimeofday: validate the values of tv fomr
 user

On Mon, 1 Dec 2014, Sasha Levin wrote:

> An unvalidated user input is multiplied by a constant, which can result in
> an undefined behaviour for large values. While this is validated later,
> we should avoid triggering undefined behaviour.
> 
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
> ---
>  kernel/time/time.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/kernel/time/time.c b/kernel/time/time.c
> index 9ec4fa5..6f53df7 100644
> --- a/kernel/time/time.c
> +++ b/kernel/time/time.c
> @@ -200,6 +200,10 @@ SYSCALL_DEFINE2(settimeofday, struct timeval __user *, tv,
>  	if (tv) {
>  		if (copy_from_user(&user_tv, tv, sizeof(*tv)))
>  			return -EFAULT;
> +
> +		if (user_tv.tv_usec > USEC_PER_SEC || user_tv.tv_usec < 0)
> +			return -EINVAL;

We should create timeval_valid() for this with the same logic as
timespec_valid().

Thanks,

	tglx

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