linux-kernel - Re: [PATCH 14/18] kdb_support: change strncpy+truncation to strlcpy

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Message-ID: <20180713151851.GA14190@nautica>
Date:   Fri, 13 Jul 2018 17:18:51 +0200
From:   Dominique Martinet <asmadeus@...ewreck.org>
To:     Daniel Thompson <daniel.thompson@...aro.org>,
        David Laight <David.Laight@...LAB.COM>
Cc:     Jason Wessel <jason.wessel@...driver.com>,
        Arnd Bergmann <arnd@...db.de>,
        kgdb-bugreport@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 14/18] kdb_support: change strncpy+truncation to strlcpy

Daniel Thompson wrote on Fri, Jul 13, 2018:
> On Fri, Jul 13, 2018 at 03:25:58AM +0200, Dominique Martinet wrote:
> > Generated by scripts/coccinelle/misc/strncpy_truncation.cocci
> > 
> > Signed-off-by: Dominique Martinet <asmadeus@...ewreck.org>
> 
> It would have been good for you to mention in the changelog how
> you reviewed your change to verify that the extra zero padding
> from strncpy() isn't required.

I'm sorry, I went a bit too fast with the send-email button on this
path series; I agree it is lacking.

> However... I have taken a look and can't see any problem so:
> 
> Reviewed-by: Daniel Thompson <daniel.thompson@...aro.org>

Thank you for the review, I will update the commit message with more
details and change strlcpy to strscpy in a v2


David Laight wrote on Fri, Jul 13, 2018:
>    > - strncpy(knt1, symtab->sym_name, knt1_size);
>    > - knt1[knt1_size-1] = '\0';
>    > + strlcpy(knt1, symtab->sym_name, knt1_size);
>
>    You'd be better using strscpy() not strlcpy().
>    The return value of strlcpy() is the length of the source string.
>    If the source string isn't '\0' terminated horrid things happen.

I was suggested to use strlcpy for drm and didn't realize this at this
point, but you are correct; strlcpy is far from being as protective.

I'll update the coccinelle patch to use strscpy and resend this.


>    David
> 
>    Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes,
>    MK1 1PT, UK
>    Registration No: 1397386 (Wales)
> 
>    P Please consider the environment and don't print this e-mail unless
>    you really need to

(By the way, your e-mail client sends both html and text, but the text
version only included the footer so my mail client, which prefers text,
was displaying an empty mail message. If possible I would appreciate if
you could disable either version so as to get a coherent message)

-- 
Dominique Martinet