linux-kernel - Re: [PATCH net-next v3 08/10] net: pktgen: fix access outside of user given buffer in pktgen_if

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Message-ID: <914e488e-af7d-4301-8be2-410db5325f14@redhat.com>
Date: Tue, 4 Feb 2025 11:40:21 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Peter Seiderer <ps.report@....net>, netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
 "David S . Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Simon Horman <horms@...nel.org>, Shuah Khan <shuah@...nel.org>,
 Nam Cao <namcao@...utronix.de>, Thomas Gleixner <tglx@...utronix.de>,
 Frederic Weisbecker <frederic@...nel.org>,
 Artem Chernyshev <artem.chernyshev@...-soft.ru>
Subject: Re: [PATCH net-next v3 08/10] net: pktgen: fix access outside of user
 given buffer in pktgen_if_write()

Hi,

On 2/3/25 6:01 PM, Peter Seiderer wrote:
> @@ -806,6 +812,9 @@ static long num_arg(const char __user *user_buffer, unsigned long maxlen,
>  		if ((c >= '0') && (c <= '9')) {
>  			*num *= 10;
>  			*num += c - '0';
> +		} else if (i == 0) {
> +			// no valid character parsed, error out

Minor nit: please don't use C99 comments, even for single line one.

> +			return -EINVAL;
>  		} else
>  			break;
>  	}
> @@ -816,6 +825,9 @@ static int strn_len(const char __user * user_buffer, unsigned int maxlen)
>  {
>  	int i;
>  
> +	if (!maxlen)
> +		return -EINVAL;

It looks like this check is not needed? strn_len() will return 0 and the
caller will read 0 bytes from the user_buffer.

> @@ -882,39 +897,45 @@ static ssize_t get_imix_entries(const char __user *buffer,
>  		pkt_dev->imix_entries[pkt_dev->n_imix_entries].weight = weight;
>  
>  		i += len;
> +		pkt_dev->n_imix_entries++;
> +
> +		if (i >= maxlen)
> +			break;
>  		if (get_user(c, &buffer[i]))
>  			return -EFAULT;
> -
>  		i++;
> -		pkt_dev->n_imix_entries++;
>  	} while (c == ' ');
>  
>  	return i;
>  }
>  
> -static ssize_t get_labels(const char __user *buffer, struct pktgen_dev *pkt_dev)
> +static ssize_t get_labels(const char __user *buffer, int maxlen, struct pktgen_dev *pkt_dev)
>  {
>  	unsigned int n = 0;
>  	char c;
> -	ssize_t i = 0;
> -	int len;
> +	int i = 0, max, len;

Minor nit: since you are touching the variables declaration, please fix
them to respect the reverse christmas tree order.

This patch is quite large and mixes several things. I'll split out at
least the strn_len() caller fixes (possibly even the num_arg() and
hex32_arg() ones) and the refactoring in pktgen_if_write().

/P