On Mon, 23 Mar 2026 10:51:44 +0200
Andy Shevchenko <[email protected]> wrote:
> On Fri, Mar 20, 2026 at 05:48:44PM -0700, Kees Cook wrote:
> > In preparation for removing the strlcat API[1], replace the char *pp_buf
> > with a struct seq_buf, which tracks the current write position and
> > remaining space internally. This allows for:
> >
> > - Direct use of seq_buf_printf() in place of snprintf()+strlcat()
> > pairs, eliminating local tmp buffers throughout.
> > - Adjacent strlcat() calls that build strings piece-by-piece
> > (e.g., strlcat("["); strlcat(name); strlcat("]")) to be collapsed
> > into single seq_buf_printf() calls.
> > - Simpler call sites: seq_buf_puts() takes only the buffer and string,
> > with no need to pass PAGE_SIZE at every call.
> >
> > The backing buffer allocation is unchanged (__get_free_page), and the
> > output path uses seq_buf_str() to NUL-terminate before passing to
> > printk().
>
> Thanks a lot! A few comments below.
> Personally I'm in favour of this patch as it also removes a lot of ugly code
> (which is scoped string manipulations), FWIW,
> Reviewed-by: Andy Shevchenko <[email protected]>
>
> > Link: https://github.com/KSPP/linux/issues/370 [1]
>
> > Cc: Andy Shevchenko <[email protected]>
> > Cc: Josh Law <[email protected]>
>
> While not long, this still can be placed...
>
> > Signed-off-by: Kees Cook <[email protected]>
> > ---
>
> ...somewhere here to reduce unneeded noise in the commit message.
>
> > I couldn't help myself. Here's the full patch, as I suggested in
> > https://lore.kernel.org/lkml/202603201230.74BBFFABAD@keescook/
> > There are plenty more like this to do...
>
> Indeed, but thanks for the example on how to do that!
>
...
> But probably okay as in the previous branch it needs more work to follow,
> something like
>
> char dostype[8];
> ...
> if (dostype[3] < ' ') {
> /* Escape control character */
> dostype[4] = dostype[3] + '@';
> dostype[3] = '^';
> seq_buf_printf(&state->pp_buf, " (%.5s)",
> dostype);
Or just:
seq_buf_printf(&state->pp_buf, " (%.3s^%c)",
dostype, dostype[3] + '@');
David
> } else {
> seq_buf_printf(&state->pp_buf, " (%.4s)",
> dostype);
> }
>
> Taking how invasive is this, it might be better to done separately.
>
> > + seq_buf_printf(&state->pp_buf, "(res %d spb %d)",
> > + be32_to_cpu(pb->pb_Environment[6]),
> > + be32_to_cpu(pb->pb_Environment[4]));
> > }
> > res = 1;
>
