linux-kernel - Re: [PATCH] firmware: arm_scmi: quirk: fix write to string constant

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Message-ID: <aLa__M_VJYqxb9mc@hovoldconsulting.com>
Date: Tue, 2 Sep 2025 11:59:24 +0200
From: Johan Hovold <johan@...nel.org>
To: Sudeep Holla <sudeep.holla@....com>
Cc: Cristian Marussi <cristian.marussi@....com>, arm-scmi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org, Jan Palus <jpalus@...tmail.com>
Subject: Re: [PATCH] firmware: arm_scmi: quirk: fix write to string constant

Hi Sudeep,

On Fri, Aug 29, 2025 at 04:29:48PM +0200, Johan Hovold wrote:
> On Fri, Aug 29, 2025 at 03:21:52PM +0200, Johan Hovold wrote:
> > The quirk version range is typically a string constant and must not be
> > modified (e.g. as it may be stored in read-only memory):
> > 
> > 	Unable to handle kernel write to read-only memory at virtual
> > 	address ffffc036d998a947
> > 
> > Fix the range parsing so that it operates on a copy of the version range
> > string, and mark all the quirk strings as const to reduce the risk of
> > introducing similar future issues.
> 
> With Jan's permission, let's add:
> 
> Reported-by: Jan Palus <jpalus@...tmail.com>
> 
> > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220437
> > Fixes: 487c407d57d6 ("firmware: arm_scmi: Add common framework to handle firmware quirks")
> > Cc: stable@...r.kernel.org	# 6.16
> > Cc: Cristian Marussi <cristian.marussi@....com>
> > Signed-off-by: Johan Hovold <johan@...nel.org>

I noticed that you picked up this fix yesterday but also that you
rewrote the commit message and switched using cleanup helpers.

Please don't do such (non-trivial) changes without making that clear
in the commit message before your Signed-off-by tag:

	[ sudeep: rewrite commit message; switch to cleanup helpers ]

In this case, you also changed the meaning so that the commit message
now reads like the sole reason that writing to string constants is wrong
is that they may reside in read-only memory.

I used "e.g." on purpose instead of listing further reasons like the
fact that string constants may be shared so that parsing of one quirk
can subtly break a later one.

Johan