netdev - Re: [PATCH] iavf: Fix null pointer dereference in iavf_print_link

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Date: Tue, 12 Dec 2023 15:20:20 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Jesse Brandeburg <jesse.brandeburg@...el.com>
Cc: Kunwu Chan <chentao@...inos.cn>, <anthony.l.nguyen@...el.com>,
 <davem@...emloft.net>, <edumazet@...gle.com>, <pabeni@...hat.com>,
 <jacob.e.keller@...el.com>, <przemyslaw.kitszel@...el.com>,
 <intel-wired-lan@...ts.osuosl.org>, <netdev@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, Kunwu Chan <kunwu.chan@...mail.com>
Subject: Re: [PATCH] iavf: Fix null pointer dereference in
 iavf_print_link_message

On Tue, 12 Dec 2023 15:05:19 -0800 Jesse Brandeburg wrote:
> On 12/12/2023 1:28 PM, Jakub Kicinski wrote:
> > On Mon, 11 Dec 2023 10:59:27 +0800 Kunwu Chan wrote:  
> >> kasprintf() returns a pointer to dynamically allocated memory
> >> which can be NULL upon failure.
> >>
> >> Fixes: 1978d3ead82c ("intel: fix string truncation warnings")  
> > 
> > No need for the allocation here, print to a buffer on the stack.  
> 
> Sure, but I think that just takes us full circle back to where we
> started. reverting this to the previous code will add back W=1 warnings.
> 
> The whole point of the commit mentioned above was to get a reasonable
> implementation that won't cause string truncation warnings. Is there
> some trick I don't know about to get an allocation which will not
> trigger snprintf and friends to print warnings from -Wformat-truncation

Hm, it'd be nice if there was a flavor of snprintf which explicitly
doesn't trigger this warning. Or perhaps a marking for the output
buffer that says "truncation OK".

Absent that, can we print to a buffer on the stack and copy?
The link message is probably meh, but automation may get quite
confused if a NIC suddenly stops reporting FW version..