Re: [PATCH net-next] bnx2x: initialize ethtool info->fw_version before use

From: Jakub Kicinski <jakub.kicinski@netronome.com>
To: Jonathan Toppins <jtoppins@redhat.com>
Cc: netdev@vger.kernel.org, Ariel Elior <aelior@marvell.com>,
	Sudarsana Kalluru <skalluru@marvell.com>,
	GR-everest-linux-l2@marvell.com,
	"David S. Miller" <davem@davemloft.net>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next] bnx2x: initialize ethtool info->fw_version before use
Date: Mon, 18 Nov 2019 14:21:20 -0800	[thread overview]
Message-ID: <20191118142120.2cec693d@cakuba.netronome.com> (raw)
In-Reply-To: <f40bcf8cd93677c12bca1f06e74385c9a5f49819.1574096873.git.jtoppins@redhat.com>

On Mon, 18 Nov 2019 12:07:53 -0500, Jonathan Toppins wrote:
> If the info->fw_version has garbage in the buffer this can lead to a BUG()
> being generated in strlcat() due to the use of strlen(). Initialize the
> buffer before use.
> 
> The use of a systemtap script can demonstrate the problem by injecting
> garbage into fw_version:

> @@ -1111,6 +1111,8 @@ static void bnx2x_get_drvinfo(struct net_device *dev,
>  	int ext_dev_info_offset;
>  	u32 mbi;
>  
> +	info->fw_version[0] = 0;
> +
>  	strlcpy(info->driver, DRV_MODULE_NAME, sizeof(info->driver));
>  	strlcpy(info->version, DRV_MODULE_VERSION, sizeof(info->version));

I don't know systemtap, so it's very unclear what you're trying to fix
here. Setting random fields of info to 0 seems pointless as the entire
structure is zeroed before the call in ethtool_get_drvinfo().

Please explain.