linux-kernel - Re: [PATCH 05/18] iio: change strncpy+truncation to strlcpy

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Date:   Sun, 22 Jul 2018 09:13:47 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Dominique Martinet <asmadeus@...ewreck.org>
Cc:     Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Lorenzo Bianconi <lorenzo.bianconi83@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/18] iio: change strncpy+truncation to strlcpy

On Mon, 16 Jul 2018 13:42:06 +0200
Dominique Martinet <asmadeus@...ewreck.org> wrote:

> Jonathan Cameron wrote on Sun, Jul 15, 2018:
> > On Fri, 13 Jul 2018 03:25:34 +0200
> > Dominique Martinet <asmadeus@...ewreck.org> wrote:  
> > > Generated by scripts/coccinelle/misc/strncpy_truncation.cocci
> > > 
> > > Signed-off-by: Dominique Martinet <asmadeus@...ewreck.org>  
> > 
> > Applied to the togreg branch of iio.git and pushed out as testing
> > for the autobuilders to play with it.  
> 
> Thanks!
> 
> I have been pointed out that strlcpy, unlike strncpy, will read past the
> size given in the input string and thus is Bad™ if the input string is
> not nul terminated.
> 
> After taking the time to check I believe this should not happen as the
> original name seems to come from a dentry's d_name after proper
> preparation (a buffer is allocated precisely for this purpose), but it
> will not hurt to wait for that version.
> 
> 
> The second reason I was waiting is that I intended to check for each
> patch if it is safe to not pad the end of the string with zeroes (to
> avoid e.g. information leaks) and that seems OK as well here after a
> quick check but I wouldn't trust my own eyes this late so I'll let you
> be judge of that if you feel like taking v1 anyway.
> 
> Otherwise, I'll recheck properly and submit a v2 with strscpy and a
> better commit message after the coccinelle script is taken for inclusion
> and doing a better check but this might take a while longer.
> 
> 
> Thanks,

In this particular case I'm fairly sure it is safe so I'll leave it as is.

Thanks,

Jonathan