linux-kernel - Re: [PATCH net] ptp: fix integer overflow in max_vclocks

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Date: Sat, 15 Jun 2024 09:05:56 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Dan Carpenter <dan.carpenter@...aro.org>, Yangbo Lu <yangbo.lu@....com>
Cc: Richard Cochran <richardcochran@...il.com>,
 "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH net] ptp: fix integer overflow in max_vclocks_store

Le 14/06/2024 à 19:31, Dan Carpenter a écrit :
> On 32bit systems, the "4 * max" multiply can overflow.  Use size_mul()
> to fix this.
> 
> Fixes: 44c494c8e30e ("ptp: track available ptp vclocks information")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
>   drivers/ptp/ptp_sysfs.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/ptp/ptp_sysfs.c b/drivers/ptp/ptp_sysfs.c
> index a15460aaa03b..bc1562fcd6c9 100644
> --- a/drivers/ptp/ptp_sysfs.c
> +++ b/drivers/ptp/ptp_sysfs.c
> @@ -296,7 +296,7 @@ static ssize_t max_vclocks_store(struct device *dev,
>   	if (max < ptp->n_vclocks)
>   		goto out;
>   
> -	size = sizeof(int) * max;
> +	size = size_mul(sizeof(int), max);
>   	vclock_index = kzalloc(size, GFP_KERNEL);

kcalloc() maybe?

>   	if (!vclock_index) {
>   		err = -ENOMEM;

Unrelated but, a few lines above, should the:
	if (max == ptp->max_vclocks)
		return count;

be after:
	if (mutex_lock_interruptible(&ptp->n_vclocks_mux))
		return -ERESTARTSYS;

as done in n_vclocks_store()?

CJ