linux-kernel - Re: [PATCH] soc: fsl: qe: Replace all non-returning strlcpy with strscpy

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Message-ID: <202307121703.D2BE6DFEE@keescook>
Date:   Wed, 12 Jul 2023 17:06:04 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Leo Li <leoyang.li@....com>
Cc:     Azeem Shaikh <azeemshaikh38@...il.com>,
        Qiang Zhao <qiang.zhao@....com>,
        "linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] soc: fsl: qe: Replace all non-returning strlcpy with
 strscpy

On Mon, Jul 10, 2023 at 04:46:50PM +0000, Leo Li wrote:
> 
> 
> > -----Original Message-----
> > From: Azeem Shaikh <azeemshaikh38@...il.com>
> > Sent: Sunday, July 9, 2023 9:36 PM
> > To: Kees Cook <keescook@...omium.org>
> > Cc: Qiang Zhao <qiang.zhao@....com>; linux-hardening@...r.kernel.org;
> > linuxppc-dev@...ts.ozlabs.org; linux-kernel@...r.kernel.org; Leo Li
> > <leoyang.li@....com>; linux-arm-kernel@...ts.infradead.org
> > Subject: Re: [PATCH] soc: fsl: qe: Replace all non-returning strlcpy with
> > strscpy
> > 
> > On Tue, May 23, 2023 at 1:20 PM Kees Cook <keescook@...omium.org>
> > wrote:
> > >
> > > On Tue, May 23, 2023 at 02:14:25AM +0000, Azeem Shaikh wrote:
> > > > strlcpy() reads the entire source buffer first.
> > > > This read may exceed the destination size limit.
> > > > This is both inefficient and can lead to linear read overflows if a
> > > > source string is not NUL-terminated [1].
> > > > In an effort to remove strlcpy() completely [2], replace
> > > > strlcpy() here with strscpy().
> > > > No return values were used, so direct replacement is safe.
> > > >
> > > > [1]
> > > >
> > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fww
> > > >
> > w.kernel.org%2Fdoc%2Fhtml%2Flatest%2Fprocess%2Fdeprecated.html%23s
> > tr
> > > >
> > lcpy&data=05%7C01%7Cleoyang.li%40nxp.com%7C11f9df1df1b5440e4ec108
> > db8
> > > >
> > 0ee64de%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C63824553360
> > 3780
> > > >
> > 889%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2lu
> > MzIiLCJB
> > > >
> > TiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=jcTy3IF37wqC1
> > MWsSuF
> > > > %2F51Z1trQEMaow7BHkPSh3hzI%3D&reserved=0
> > > > [2]
> > > > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgi
> > > >
> > thub.com%2FKSPP%2Flinux%2Fissues%2F89&data=05%7C01%7Cleoyang.li%
> > 40nx
> > > >
> > p.com%7C11f9df1df1b5440e4ec108db80ee64de%7C686ea1d3bc2b4c6fa92cd
> > 99c5
> > > >
> > c301635%7C0%7C0%7C638245533603780889%7CUnknown%7CTWFpbGZsb3d
> > 8eyJWIjo
> > > >
> > iMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C30
> > 00%7
> > > >
> > C%7C%7C&sdata=Blr0W1oYPIw5uDu7HqlEkU7xOuAo4bQNkk%2Bt%2BAuFqc
> > s%3D&res
> > > > erved=0
> > > >
> > > > Signed-off-by: Azeem Shaikh <azeemshaikh38@...il.com>
> > >
> > > Reviewed-by: Kees Cook <keescook@...omium.org>
> > >
> > 
> > Friendly ping on this.
> 
> Sorry for the late response.  But I found some old discussions with the conclusion to be not converting old users.  Has this been changed later on?
> https://lwn.net/Articles/659214/

The objection was with _mass_ conversions due to the risk of regressions
being introduced in a way that makes it hard to revert/bisect, etc.
We've being long on the road to doing these conversions to eliminate
strlcpy(), which continues to get introduced into the kernel, even
though it is risky.

-- 
Kees Cook