Re: [PATCH] sysfs: sysfs_pathname/sysfs_add_one: Use strlcat() instead of strcat()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Sat, Sep 29, 2012 at 10:23:19PM +0200, Geert Uytterhoeven wrote:
> The warning check for duplicate sysfs entries can cause a buffer overflow
> when printing the warning, as strcat() doesn't check buffer sizes.
> Use strlcat() instead.

As the comment said, we knew about this, but I have never seen it, do
you know of a way to trigger it?

> Since strlcat() doesn't return a pointer to the passed buffer, unlike
> strcat(), I had to convert the nested concatenation in sysfs_add_one() to
> an admittedly more obscure comma operator construct, to avoid emitting code
> for the concatenation if CONFIG_BUG is disabled.

That's a fun construct, nice work.

> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Cc: stable@vger.kernel.org

Given that I don't know of any way to actually hit this problem, is it
really needed for older kernel releases?

thanks,

greg k-h