[prev in list] [next in list] [prev in thread] [next in thread] 

List:       linux-hardening
Subject:    Re: [PATCH] video: fbdev: au1200fb: replace deprecated strncpy with strscpy
From:       Justin Stitt <justinstitt () google ! com>
Date:       2024-03-20 22:35:26
Message-ID: CAFhGd8ppVq9aGbfFLeL30jQ15KHS=FoLh0c1udXo=Z+pCfXL1g () mail ! gmail ! com
[Download RAW message or body]

Hi,

On Wed, Mar 20, 2024 at 12:56 AM Helge Deller <deller@gmx.de> wrote:
> 
> On 3/19/24 00:46, Justin Stitt wrote:
> > strncpy() is deprecated for use on NUL-terminated destination strings
> > [1] and as such we should prefer more robust and less ambiguous string
> > interfaces.
> > 
> > Let's use the new 2-argument strscpy() which guarantees NUL-termination
> > on the destination buffer while also simplifying the syntax. Note that
> > strscpy() will not NUL-pad the destination buffer like strncpy() does.
> > 
> > However, the NUL-padding behavior of strncpy() is not required since
> > fbdev is already NUL-allocated from au1200fb_drv_probe() ->
> > frameuffer_alloc(), rendering any additional NUL-padding redundant.
> > > p = kzalloc(fb_info_size + size, GFP_KERNEL);
> > 
> > Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings \
> >                 [1]
> > Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> > Link: https://github.com/KSPP/linux/issues/90
> > Cc: linux-hardening@vger.kernel.org
> > Signed-off-by: Justin Stitt <justinstitt@google.com>
> > ---
> > Note: build-tested only.
> > 
> > Found with: $ rg "strncpy\("
> > ---
> > drivers/video/fbdev/au1200fb.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/video/fbdev/au1200fb.c b/drivers/video/fbdev/au1200fb.c
> > index 6f20efc663d7..e718fea63662 100644
> > --- a/drivers/video/fbdev/au1200fb.c
> > +++ b/drivers/video/fbdev/au1200fb.c
> > @@ -1557,7 +1557,7 @@ static int au1200fb_init_fbinfo(struct au1200fb_device \
> > *fbdev) return ret;
> > }
> > 
> > -     strncpy(fbi->fix.id, "AU1200", sizeof(fbi->fix.id));
> > +     strscpy(fbi->fix.id, "AU1200");
> 
> I wonder if you really build-tested this, as this driver is for the mips \
> architecture... And I don't see a strscpy() function which takes just 2 arguments.
> But I might be wrong....

I did build successfully :thumbs_up:

Commit e6584c3964f2f ("string: Allow 2-argument strscpy()") introduced
this new strscpy() form; it is present in string.h on Linus' tree.

> 
> Helge

Thanks
Justin


[prev in list] [next in list] [prev in thread] [next in thread]