linux-kernel - Re: [PATCH net v2] hdlc_ppp: fix potential null pointer in ppp_cp

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Message-ID: <20251003100309.GH2878334@horms.kernel.org>
Date: Fri, 3 Oct 2025 11:03:09 +0100
From: Simon Horman <horms@...nel.org>
To: Kriish Sharma <kriish.sharma2006@...il.com>
Cc: khalasa@...p.pl, khc@...waw.pl, andrew+netdev@...n.ch,
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v2] hdlc_ppp: fix potential null pointer in
 ppp_cp_event logging

On Fri, Oct 03, 2025 at 09:29:18AM +0000, Kriish Sharma wrote:
> Fixes warnings observed during compilation with -Wformat-overflow:
> 
> drivers/net/wan/hdlc_ppp.c: In function ‘ppp_cp_event’:
> drivers/net/wan/hdlc_ppp.c:353:17: warning: ‘%s’ directive argument is null [-Wformat-overflow=]
>   353 |                 netdev_info(dev, "%s down\n", proto_name(pid));
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/wan/hdlc_ppp.c:342:17: warning: ‘%s’ directive argument is null [-Wformat-overflow=]
>   342 |                 netdev_info(dev, "%s up\n", proto_name(pid));
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Update proto_name() to return "LCP" by default instead of NULL.
> This change silences the compiler without changing existing behavior
> and removes the need for the local 'pname' variable in ppp_cp_event.
> 
> Suggested-by: Krzysztof Hałasa <khalasa@...p.pl>
> Fixes: 262858079afd ("Add linux-next specific files for 20250926")

Perhaps this should be:

Fixes: e022c2f07ae5 ("WAN: new synchronous PPP implementation for generic HDLC.")
But more importantly, and sorry for not noticing this in my review of v1,
I'm not sure this is a bug fix. In his review of v1 Chris explains that
this case cannot be hit. And that the patch is about silencing the
compiler.

If so, I'd suggest this is a clean-up and thus you should consider:
1) Removing the fixes tag
2) Retargeting the patch at net-next

Please also note that net-next is currently closed for the merge window.
So any patches for it should be sent after it reopens, which will
be after v6.18-rc1 is released, most likely on or after 13th October.

See: https://docs.kernel.org/process/maintainer-netdev.html

The code change itself looks good to me.

> Signed-off-by: Kriish Sharma <kriish.sharma2006@...il.com>
> ---
> v2:
>   - Target the net tree with proper subject prefix "[PATCH net]"
>   - Update proto_name() to return "LCP" by default instead of NULL
>   - Remove local 'pname' variable in ppp_cp_event
>   - Add Suggested-by tag for Krzysztof Hałasa
> 
> v1: https://lore.kernel.org/all/20251002180541.1375151-1-kriish.sharma2006@gmail.com/
>