From: Kent Overstreet <kent.overstreet@linux.dev>
To: Kees Cook <keescook@chromium.org>
Cc: Suren Baghdasaryan <surenb@google.com>,
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Subject: Re: [PATCH v4 14/36] lib: add allocation tagging support for memory allocation profiling
Date: Wed, 21 Feb 2024 19:34:44 -0500 [thread overview]
Message-ID: <vxx2o2wdcqjkxauglu7ul52mygu4tti2i3yc2dvmcbzydvgvu2@knujflwtakni> (raw)
In-Reply-To: <202402211608.41AD94094@keescook>
On Wed, Feb 21, 2024 at 04:25:02PM -0800, Kees Cook wrote:
> On Wed, Feb 21, 2024 at 06:29:17PM -0500, Kent Overstreet wrote:
> > 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?
>
> Yes, very very much. One of the worst and mostly unaddressed weaknesses
> with the kernel right now is use-after-free based type confusion[0], which
> depends on merged caches (or cache reuse).
>
> This doesn't solve cross-allocator (kmalloc/page_alloc) type confusion
> (as terrifyingly demonstrated[1] by Jann Horn), but it does help with
> what has been a very common case of "use msg_msg to impersonate your
> target object"[2] exploitation.
We have a ton of code that references PAGE_SIZE and uses the page
allocator completely unnecessarily - that's something worth harping
about at conferences; if we could motivate people to clean that stuff up
it'd have a lot of positive effects.
> > That would produce a _lot_ of kmem caches
>
> Fewer than you'd expect, but yes, there is some overhead. However,
> out-of-tree forks of Linux have successfully experimented with this
> already and seen good results[3].
So in that case - I don't think there's any need for a separate
alloc_details; we'd just add a kmem_cache * to alloc_tag and then hook
into the codetag init/unload path to create and destroy the kmem caches.
No need to adjust the slab code either; alloc_hooks() itself could
dispatch to kmem_cache_alloc() instead of kmalloc() if this is in use.
next prev parent reply other threads:[~2024-02-22 0:34 UTC|newest]
Thread overview: 97+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-21 19:40 [PATCH v4 00/36] Memory allocation profiling Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 01/36] fix missing vmalloc.h includes Suren Baghdasaryan
2024-02-21 21:09 ` Pasha Tatashin
2024-02-21 19:40 ` [PATCH v4 02/36] asm-generic/io.h: Kill vmalloc.h dependency Suren Baghdasaryan
2024-02-21 21:11 ` Pasha Tatashin
2024-02-21 19:40 ` [PATCH v4 03/36] mm/slub: Mark slab_free_freelist_hook() __always_inline Suren Baghdasaryan
2024-02-21 21:15 ` Pasha Tatashin
2024-02-24 2:02 ` Suren Baghdasaryan
2024-02-26 14:31 ` Vlastimil Babka
[not found] ` <CA+CK2bBggtq6M96Pu49BmG_j01Sv6p_84Go++9APuvVPXHMwvQ@mail.gmail.com>
2024-02-26 16:09 ` Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 04/36] scripts/kallysms: Always include __start and __stop symbols Suren Baghdasaryan
2024-02-21 21:20 ` Pasha Tatashin
2024-02-21 19:40 ` [PATCH v4 05/36] fs: Convert alloc_inode_sb() to a macro Suren Baghdasaryan
2024-02-21 21:23 ` Pasha Tatashin
2024-02-26 15:44 ` Vlastimil Babka
2024-02-26 17:48 ` Suren Baghdasaryan
2024-02-26 20:50 ` Kent Overstreet
2024-02-21 19:40 ` [PATCH v4 06/36] mm: enumerate all gfp flags Suren Baghdasaryan
2024-02-21 21:25 ` Pasha Tatashin
2024-02-22 12:12 ` Michal Hocko
2024-02-22 12:24 ` Petr Tesařík
2024-02-23 19:26 ` Suren Baghdasaryan
2024-02-24 1:59 ` Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 07/36] mm: introduce slabobj_ext to support slab object extensions Suren Baghdasaryan
2024-02-21 21:30 ` Pasha Tatashin
2024-02-26 16:26 ` Vlastimil Babka
2024-02-26 17:22 ` Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 08/36] mm: introduce __GFP_NO_OBJ_EXT flag to selectively prevent slabobj_ext creation Suren Baghdasaryan
2024-02-22 0:08 ` Pasha Tatashin
2024-02-26 16:51 ` Vlastimil Babka
2024-02-21 19:40 ` [PATCH v4 09/36] mm/slab: introduce SLAB_NO_OBJ_EXT to avoid obj_ext creation Suren Baghdasaryan
2024-02-22 0:09 ` Pasha Tatashin
2024-02-26 16:52 ` Vlastimil Babka
2024-02-21 19:40 ` [PATCH v4 10/36] slab: objext: introduce objext_flags as extension to page_memcg_data_flags Suren Baghdasaryan
2024-02-22 0:12 ` Pasha Tatashin
2024-02-26 16:53 ` Vlastimil Babka
2024-02-21 19:40 ` [PATCH v4 11/36] lib: code tagging framework Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 12/36] lib: code tagging module support Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 13/36] lib: prevent module unloading if memory is not freed Suren Baghdasaryan
2024-02-26 16:58 ` Vlastimil Babka
2024-02-26 17:13 ` Suren Baghdasaryan
2024-03-12 18:23 ` Luis Chamberlain
2024-03-12 19:56 ` Suren Baghdasaryan
2024-03-12 20:07 ` Kent Overstreet
2024-02-21 19:40 ` [PATCH v4 14/36] lib: add allocation tagging support for memory allocation profiling Suren Baghdasaryan
2024-02-21 23:05 ` Kees Cook
2024-02-21 23:29 ` Kent Overstreet
2024-02-22 0:25 ` Kees Cook
2024-02-22 0:34 ` Kent Overstreet [this message]
2024-02-22 0:57 ` Kees Cook
2024-02-28 8:29 ` Vlastimil Babka
2024-02-28 18:05 ` Suren Baghdasaryan
2024-02-28 8:41 ` Vlastimil Babka
2024-02-28 18:07 ` Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 15/36] lib: introduce support for page allocation tagging Suren Baghdasaryan
2024-02-26 17:07 ` Vlastimil Babka
2024-02-26 17:11 ` Suren Baghdasaryan
2024-02-27 9:30 ` Vlastimil Babka
2024-02-27 9:45 ` Kent Overstreet
2024-02-27 16:55 ` Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 16/36] mm: percpu: increase PERCPU_MODULE_RESERVE to accommodate allocation tags Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 17/36] change alloc_pages name in dma_map_ops to avoid name conflicts Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 18/36] mm: enable page allocation tagging Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 19/36] mm: create new codetag references during page splitting Suren Baghdasaryan
2024-02-27 10:11 ` Vlastimil Babka
2024-02-27 16:38 ` Suren Baghdasaryan
2024-02-28 8:47 ` Vlastimil Babka
2024-02-28 17:50 ` Suren Baghdasaryan
2024-02-28 18:28 ` Vlastimil Babka
2024-02-28 18:38 ` Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 20/36] mm/page_ext: enable early_page_ext when CONFIG_MEM_ALLOC_PROFILING_DEBUG=y Suren Baghdasaryan
2024-02-27 10:18 ` Vlastimil Babka
2024-02-21 19:40 ` [PATCH v4 21/36] lib: add codetag reference into slabobj_ext Suren Baghdasaryan
2024-02-27 10:19 ` Vlastimil Babka
2024-02-21 19:40 ` [PATCH v4 22/36] mm/slab: add allocation accounting into slab allocation and free paths Suren Baghdasaryan
2024-02-27 13:07 ` Vlastimil Babka
2024-02-27 16:15 ` Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 23/36] mm/slab: enable slab allocation tagging for kmalloc and friends Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 24/36] rust: Add a rust helper for krealloc() Suren Baghdasaryan
2024-02-22 9:59 ` Alice Ryhl
2024-02-23 22:17 ` Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 25/36] mempool: Hook up to memory allocation profiling Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 26/36] mm: percpu: Introduce pcpuobj_ext Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 27/36] mm: percpu: Add codetag reference into pcpuobj_ext Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 28/36] mm: percpu: enable per-cpu allocation tagging Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 29/36] mm: vmalloc: Enable memory allocation profiling Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 30/36] rhashtable: Plumb through alloc tag Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 31/36] lib: add memory allocations report in show_mem() Suren Baghdasaryan
2024-02-27 13:19 ` Vlastimil Babka
2024-02-27 16:12 ` Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 32/36] codetag: debug: skip objext checking when it's for objext itself Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 33/36] codetag: debug: mark codetags for reserved pages as empty Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 34/36] codetag: debug: introduce OBJEXTS_ALLOC_FAIL to mark failed slab_ext allocations Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 35/36] MAINTAINERS: Add entries for code tagging and memory allocation profiling Suren Baghdasaryan
2024-02-21 19:40 ` [PATCH v4 36/36] memprofiling: Documentation Suren Baghdasaryan
2024-02-27 13:36 ` [PATCH v4 00/36] Memory allocation profiling Vlastimil Babka
2024-02-27 16:10 ` Suren Baghdasaryan
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