linux-kernel - Re: [PATCH net-next v3 3/5] dpll: zl3073x: Add firmware loading functionality

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Message-ID: <20250829165218.4d597b8b@kernel.org>
Date: Fri, 29 Aug 2025 16:52:18 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Ivan Vecera <ivecera@...hat.com>
Cc: netdev@...r.kernel.org, Jiri Pirko <jiri@...nulli.us>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
 <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, Jonathan Corbet
 <corbet@....net>, Prathosh Satish <Prathosh.Satish@...rochip.com>,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, Michal Schmidt
 <mschmidt@...hat.com>, Petr Oros <poros@...hat.com>, Przemek Kitszel
 <przemyslaw.kitszel@...el.com>
Subject: Re: [PATCH net-next v3 3/5] dpll: zl3073x: Add firmware loading
 functionality

On Fri, 29 Aug 2025 12:39:30 +0200 Ivan Vecera wrote:
> >> +	strscpy(buf, *psrc, min(sizeof(buf), *psize));
> >> +	rc = sscanf(buf, "%15s %u %n", name, &count, &pos);
> >> +	if (!rc) {
> >> +		/* No more data */
> >> +		return 0;
> >> +	} else if (rc == 1) {
> >> +		ZL3073X_FW_ERR_MSG(zldev, extack, "invalid component size");
> >> +		return -EINVAL;
> >> +	}
> >> +	*psrc += pos;
> >> +	*psize -= pos;  
> > 
> > what if pos > *psize ? I think the parsing needs more care.  
> 
> This should not happen. strscpy copies min(32, *psize) from the source
> to buf and sscanf parses buf and fills pos by index from the buf.
> The pos cannot be greater than *psize...or did I miss something?

Glancing at it now, I think I was concerned that *psize will go
negative / wrap. So potentially leading to over-read of psrc,
rather than overflow of buf. But I could well be wrong..