Re: [PATCH] string: Improve the generic strlcpy() implementation

[Ingo Molnar <mingo@kernel.org>]

* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> > 2) strscpy() will copy garbage past NUL from source into destination. It won't 
> > fault but still, who knows what lies after string.
> 
> Yes, that's probably worth fixing before we get actual users..

Hm, this is the spot:

                c = *(unsigned long *)(src+res);
                *(unsigned long *)(dest+res) = c;

                if (has_zero(c, &data, &constants)) {
                        data = prep_zero_mask(c, data, &constants);
                        data = create_zero_mask(data);
                        return res + find_zero(data);
                }

We could do something like:

                c = *(unsigned long *)(src+res);
                *(unsigned long *)(dest+res) = c;

                if (has_zero(c, &data, &constants)) {
			unsigned int zero_pos;

                        data = prep_zero_mask(c, data, &constants);
                        data = create_zero_mask(data);

			zero_pos = find_zero(data);
			res += zero_pos;

			memset(dest+res, 0, sizeof(long)-zero_pos);

                        return res;
                }

I.e. the extra memset() clears out the partial word (if any) after the NUL.

Completely untested.

Thanks,

	Ingo