Re: [PATCH 3.2 090/152] time: adjtimex: Validate the ADJ_FREQUENCY values

[Luis Henriques <luis.henriques@canonical.com>]

On Tue, Feb 17, 2015 at 01:46:53AM +0000, Ben Hutchings wrote:
> 3.2.67-rc1 review patch.  If anyone has any objections, please let me know.
>

John reported a regression with this commit [1].  A fix seems to be
already available, but since it hasn't been accepted into mainline yet
I haven't picked this patch for the 3.16 kernel.

[1] https://lists.ubuntu.com/archives/kernel-team/2015-February/053981.html

Cheers,
--
Luís

> ------------------
> 
> From: Sasha Levin <sasha.levin@oracle.com>
> 
> commit 5e5aeb4367b450a28f447f6d5ab57d8f2ab16a5f upstream.
> 
> Verify that the frequency value from userspace is valid and makes sense.
> 
> Unverified values can cause overflows later on.
> 
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@kernel.org>
> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
> [jstultz: Fix up bug for negative values and drop redunent cap check]
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> [bwh: Backported to 3.2: adjust context]
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> ---
>  kernel/time/ntp.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> --- a/kernel/time/ntp.c
> +++ b/kernel/time/ntp.c
> @@ -608,6 +608,13 @@ int do_adjtimex(struct timex *txc)
>  			return -EINVAL;
>  	}
>  
> +	if (txc->modes & ADJ_FREQUENCY) {
> +		if (LONG_MIN / PPM_SCALE > txc->freq)
> +			return -EINVAL;
> +		if (LONG_MAX / PPM_SCALE < txc->freq)
> +			return -EINVAL;
> +	}
> +
>  	if (txc->modes & ADJ_SETOFFSET) {
>  		struct timespec delta;
>  		delta.tv_sec  = txc->time.tv_sec;
> 
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