netdev - Re: [PATCH net v2] amd-xgbe: do not double read link status

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250630181225.38a67e11@kernel.org>
Date: Mon, 30 Jun 2025 18:12:25 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Raju Rangoju <Raju.Rangoju@....com>
Cc: <andrew+netdev@...n.ch>, <davem@...emloft.net>, <edumazet@...gle.com>,
 <pabeni@...hat.com>, <netdev@...r.kernel.org>, <Shyam-sundar.S-k@....com>
Subject: Re: [PATCH net v2] amd-xgbe: do not double read link status

On Wed, 25 Jun 2025 15:23:15 +0530 Raju Rangoju wrote:
> The link status is latched low so that momentary link drops
> can be detected. Avoid double-reading the status to identify
> short link interruptions, unless the link was already down.

Took me a minute to understand this. How about:

The link status is latched low so that momentary link drops
can be detected. Always double-reading the status defeats this
design feature. Only double read if link was already down.

> -	reg = XMDIO_READ(pdata, MDIO_MMD_PCS, MDIO_STAT1);
> -	reg = XMDIO_READ(pdata, MDIO_MMD_PCS, MDIO_STAT1);
> +	if (!pdata->phy.link) {
> +		reg = XMDIO_READ(pdata, MDIO_MMD_PCS, MDIO_STAT1);
> +		if (reg < 0)
> +			return reg;
> +
> +		if (reg & MDIO_STAT1_LSTATUS)
> +			goto skip_read;
> +	}
>  
> +	reg = XMDIO_READ(pdata, MDIO_MMD_PCS, MDIO_STAT1);
> +	if (reg < 0)
> +		return reg;
> +skip_read:
>  	if (pdata->en_rx_adap) {
>  		/* if the link is available and adaptation is done,
>  		 * declare link up

Don't use gotos for normal function control flow :/

	reg = XMDIO_READ(pdata, MDIO_MMD_PCS, MDIO_STAT1);
	if (reg < 0)
		return reg;
	/* Link status is latched low so that momentary link drops
	 * can be detected. If link was already down read again
	 * to get the latest state.
 	 */
	if (!pdata->phy.link && !(reg & MDIO_STAT1_LSTATUS)) {
 		reg = XMDIO_READ(pdata, MDIO_MMD_PCS, MDIO_STAT1);
		if (reg < 0)
			return reg;
	}

	if (pdata->en_rx_adap) {
 		/* if the link is available and adaptation is done,
-- 
pw-bot: cr