linux-kernel - Re: [PATCH v4 14/36] lib: add allocation tagging support for memory allocation profiling

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date: Wed, 21 Feb 2024 18:29:17 -0500
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Kees Cook <keescook@...omium.org>
Cc: Suren Baghdasaryan <surenb@...gle.com>, akpm@...ux-foundation.org, 
	mhocko@...e.com, vbabka@...e.cz, hannes@...xchg.org, roman.gushchin@...ux.dev, 
	mgorman@...e.de, dave@...olabs.net, willy@...radead.org, liam.howlett@...cle.com, 
	penguin-kernel@...ove.sakura.ne.jp, corbet@....net, void@...ifault.com, peterz@...radead.org, 
	juri.lelli@...hat.com, catalin.marinas@....com, will@...nel.org, arnd@...db.de, 
	tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com, x86@...nel.org, 
	peterx@...hat.com, david@...hat.com, axboe@...nel.dk, mcgrof@...nel.org, 
	masahiroy@...nel.org, nathan@...nel.org, dennis@...nel.org, tj@...nel.org, 
	muchun.song@...ux.dev, rppt@...nel.org, paulmck@...nel.org, pasha.tatashin@...een.com, 
	yosryahmed@...gle.com, yuzhao@...gle.com, dhowells@...hat.com, hughd@...gle.com, 
	andreyknvl@...il.com, ndesaulniers@...gle.com, vvvvvv@...gle.com, 
	gregkh@...uxfoundation.org, ebiggers@...gle.com, ytcoode@...il.com, 
	vincent.guittot@...aro.org, dietmar.eggemann@....com, rostedt@...dmis.org, 
	bsegall@...gle.com, bristot@...hat.com, vschneid@...hat.com, cl@...ux.com, 
	penberg@...nel.org, iamjoonsoo.kim@....com, 42.hyeyoo@...il.com, glider@...gle.com, 
	elver@...gle.com, dvyukov@...gle.com, shakeelb@...gle.com, 
	songmuchun@...edance.com, jbaron@...mai.com, rientjes@...gle.com, minchan@...gle.com, 
	kaleshsingh@...gle.com, kernel-team@...roid.com, linux-doc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, iommu@...ts.linux.dev, linux-arch@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, linux-modules@...r.kernel.org, 
	kasan-dev@...glegroups.com, cgroups@...r.kernel.org
Subject: Re: [PATCH v4 14/36] lib: add allocation tagging support for memory
 allocation profiling

On Wed, Feb 21, 2024 at 03:05:32PM -0800, Kees Cook wrote:
> On Wed, Feb 21, 2024 at 11:40:27AM -0800, Suren Baghdasaryan wrote:
> > [...]
> > +struct alloc_tag {
> > +	struct codetag			ct;
> > +	struct alloc_tag_counters __percpu	*counters;
> > +} __aligned(8);
> > [...]
> > +#define DEFINE_ALLOC_TAG(_alloc_tag)						\
> > +	static DEFINE_PER_CPU(struct alloc_tag_counters, _alloc_tag_cntr);	\
> > +	static struct alloc_tag _alloc_tag __used __aligned(8)			\
> > +	__section("alloc_tags") = {						\
> > +		.ct = CODE_TAG_INIT,						\
> > +		.counters = &_alloc_tag_cntr };
> > [...]
> > +static inline struct alloc_tag *alloc_tag_save(struct alloc_tag *tag)
> > +{
> > +	swap(current->alloc_tag, tag);
> > +	return tag;
> > +}
> 
> Future security hardening improvement idea based on this infrastructure:
> it should be possible to implement per-allocation-site kmem caches. For
> example, we could create:
> 
> struct alloc_details {
> 	u32 flags;
> 	union {
> 		u32 size; /* not valid after __init completes */
> 		struct kmem_cache *cache;
> 	};
> };
> 
> - add struct alloc_details to struct alloc_tag
> - move the tags section into .ro_after_init
> - extend alloc_hooks() to populate flags and size:
> 	.flags = __builtin_constant_p(size) ? KMALLOC_ALLOCATE_FIXED
> 					    : KMALLOC_ALLOCATE_BUCKETS;
> 	.size = __builtin_constant_p(size) ? size : SIZE_MAX;
> - during kernel start or module init, walk the alloc_tag list
>   and create either a fixed-size kmem_cache or to allocate a
>   full set of kmalloc-buckets, and update the "cache" member.
> - adjust kmalloc core routines to use current->alloc_tag->cache instead
>   of using the global buckets.
> 
> This would get us fully separated allocations, producing better than
> type-based levels of granularity, exceeding what we have currently with
> CONFIG_RANDOM_KMALLOC_CACHES.
> 
> Does this look possible, or am I misunderstanding something in the
> infrastructure being created here?

Definitely possible, but... would we want this? That would produce a
_lot_ of kmem caches, and don't we already try to collapse those where
possible to reduce internal fragmentation?