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Message-ID: <202409111518.FFAD85919@keescook> Date: Wed, 11 Sep 2024 15:18:44 -0700 From: Kees Cook <kees@...nel.org> To: Suren Baghdasaryan <surenb@...gle.com> Cc: Vlastimil Babka <vbabka@...e.cz>, Kent Overstreet <kent.overstreet@...ux.dev>, Christoph Lameter <cl@...ux.com>, Pekka Enberg <penberg@...nel.org>, David Rientjes <rientjes@...gle.com>, Joonsoo Kim <iamjoonsoo.kim@....com>, Andrew Morton <akpm@...ux-foundation.org>, Roman Gushchin <roman.gushchin@...ux.dev>, Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-mm@...ck.org, "GONG, Ruiqi" <gongruiqi@...weicloud.com>, Jann Horn <jannh@...gle.com>, Matteo Rizzo <matteorizzo@...gle.com>, jvoisin <julien.voisin@...tri.org>, Xiu Jianfeng <xiujianfeng@...wei.com>, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: Re: [PATCH 3/5] codetag: Introduce codetag_early_walk() On Thu, Aug 29, 2024 at 08:39:29AM -0700, Suren Baghdasaryan wrote: > On Fri, Aug 9, 2024 at 12:33 AM Kees Cook <kees@...nel.org> wrote: > > > > In order to process builtin alloc_tags much earlier during boot (before > > register_codetag() is processed), provide codetag_early_walk() that > > perform a lockless walk with a specified callback function. This will be > > used to allocate required caches that cannot be allocated on demand. > > > > Signed-off-by: Kees Cook <kees@...nel.org> > > --- > > Cc: Suren Baghdasaryan <surenb@...gle.com> > > Cc: Kent Overstreet <kent.overstreet@...ux.dev> > > Cc: Vlastimil Babka <vbabka@...e.cz> > > Cc: Christoph Lameter <cl@...ux.com> > > Cc: Pekka Enberg <penberg@...nel.org> > > Cc: David Rientjes <rientjes@...gle.com> > > Cc: Joonsoo Kim <iamjoonsoo.kim@....com> > > Cc: Andrew Morton <akpm@...ux-foundation.org> > > Cc: Roman Gushchin <roman.gushchin@...ux.dev> > > Cc: Hyeonggon Yoo <42.hyeyoo@...il.com> > > Cc: linux-mm@...ck.org > > --- > > include/linux/codetag.h | 2 ++ > > lib/codetag.c | 16 ++++++++++++++++ > > 2 files changed, 18 insertions(+) > > > > diff --git a/include/linux/codetag.h b/include/linux/codetag.h > > index c2a579ccd455..9eb1fcd90570 100644 > > --- a/include/linux/codetag.h > > +++ b/include/linux/codetag.h > > @@ -64,6 +64,8 @@ void codetag_lock_module_list(struct codetag_type *cttype, bool lock); > > bool codetag_trylock_module_list(struct codetag_type *cttype); > > struct codetag_iterator codetag_get_ct_iter(struct codetag_type *cttype); > > struct codetag *codetag_next_ct(struct codetag_iterator *iter); > > +void codetag_early_walk(const struct codetag_type_desc *desc, > > + void (*callback)(struct codetag *ct)); > > > > void codetag_to_text(struct seq_buf *out, struct codetag *ct); > > > > diff --git a/lib/codetag.c b/lib/codetag.c > > index ef7634c7ee18..9d563c8c088a 100644 > > --- a/lib/codetag.c > > +++ b/lib/codetag.c > > @@ -154,6 +154,22 @@ static struct codetag_range get_section_range(struct module *mod, > > }; > > } > > > > +void codetag_early_walk(const struct codetag_type_desc *desc, > > + void (*callback)(struct codetag *ct)) > > +{ > > + struct codetag_range range; > > + struct codetag *ct; > > + > > + range = get_section_range(NULL, desc->section); > > + if (!range.start || !range.stop || > > + range.start == range.stop || > > + range.start > range.stop) > > + return; > > I think this check can be simplified to: > > if (!range.start || range.start >= range.stop) > return; > > nit: Technically (!range.start) should also never trigger. In a valid > image these symbols are either missing (range.start == range.stop == > NULL) or both are defined and (range.start < range.stop). Yeah, all true. I was mainly copying all the checks that existed in the "slow path" version. I will adjust this for the next version. -- Kees Cook
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