From: Kees Cook <keescook@chromium.org>
To: Matteo Rizzo <matteorizzo@google.com>
Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com,
iamjoonsoo.kim@lge.com, akpm@linux-foundation.org,
vbabka@suse.cz, roman.gushchin@linux.dev, 42.hyeyoo@gmail.com,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-mm@kvack.org, linux-hardening@vger.kernel.org,
tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com,
corbet@lwn.net, luto@kernel.org, peterz@infradead.org,
jannh@google.com, evn@google.com, poprdi@google.com,
jordyzomer@google.com
Subject: Re: [RFC PATCH 01/14] mm/slub: don't try to dereference invalid freepointers
Date: Fri, 15 Sep 2023 13:50:00 -0700 [thread overview]
Message-ID: <202309151349.BEBA203D@keescook> (raw)
In-Reply-To: <20230915105933.495735-2-matteorizzo@google.com>
On Fri, Sep 15, 2023 at 10:59:20AM +0000, Matteo Rizzo wrote:
> slab_free_freelist_hook tries to read a freelist pointer from the
> current object even when freeing a single object. This is invalid
> because single objects don't actually contain a freelist pointer when
> they're freed and the memory contains other data. This causes problems
> for checking the integrity of freelist in get_freepointer.
>
> Signed-off-by: Matteo Rizzo <matteorizzo@google.com>
> ---
> mm/slub.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index f7940048138c..a7dae207c2d2 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -1820,7 +1820,9 @@ static inline bool slab_free_freelist_hook(struct kmem_cache *s,
>
> do {
> object = next;
> - next = get_freepointer(s, object);
> + /* Single objects don't actually contain a freepointer */
> + if (object != old_tail)
> + next = get_freepointer(s, object);
>
> /* If object's reuse doesn't have to be delayed */
> if (!slab_free_hook(s, object, slab_want_init_on_free(s))) {
I find this loop's logic a bit weird, but, yes, this ends up being
correct and avoids needless work.
Reviewed-by: Kees Cook <keescook@chromium.org>
--
Kees Cook
next prev parent reply other threads:[~2023-09-15 20:50 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-15 10:59 [RFC PATCH 00/14] Prevent cross-cache attacks in the SLUB allocator Matteo Rizzo
2023-09-15 10:59 ` [RFC PATCH 01/14] mm/slub: don't try to dereference invalid freepointers Matteo Rizzo
2023-09-15 20:50 ` Kees Cook [this message]
2023-09-30 11:04 ` Hyeonggon Yoo
2023-09-15 10:59 ` [RFC PATCH 02/14] mm/slub: add is_slab_addr/is_slab_page helpers Matteo Rizzo
2023-09-15 20:55 ` Kees Cook
2023-09-15 10:59 ` [RFC PATCH 03/14] mm/slub: move kmem_cache_order_objects to slab.h Matteo Rizzo
2023-09-15 20:56 ` Kees Cook
2023-09-15 10:59 ` [RFC PATCH 04/14] mm: use virt_to_slab instead of folio_slab Matteo Rizzo
2023-09-15 20:59 ` Kees Cook
2023-09-15 10:59 ` [RFC PATCH 05/14] mm/slub: create folio_set/clear_slab helpers Matteo Rizzo
2023-09-15 21:02 ` Kees Cook
2023-09-15 10:59 ` [RFC PATCH 06/14] mm/slub: pass additional args to alloc_slab_page Matteo Rizzo
2023-09-15 21:03 ` Kees Cook
2023-09-15 10:59 ` [RFC PATCH 07/14] mm/slub: pass slab pointer to the freeptr decode helper Matteo Rizzo
2023-09-15 21:06 ` Kees Cook
2023-09-15 10:59 ` [RFC PATCH 08/14] security: introduce CONFIG_SLAB_VIRTUAL Matteo Rizzo
2023-09-15 21:07 ` Kees Cook
2023-09-15 10:59 ` [RFC PATCH 09/14] mm/slub: add the slab freelists to kmem_cache Matteo Rizzo
2023-09-15 21:08 ` Kees Cook
2023-09-15 10:59 ` [RFC PATCH 10/14] x86: Create virtual memory region for SLUB Matteo Rizzo
2023-09-15 21:13 ` Kees Cook
2023-09-15 21:49 ` Dave Hansen
2023-09-18 8:54 ` Matteo Rizzo
2023-09-15 10:59 ` [RFC PATCH 11/14] mm/slub: allocate slabs from virtual memory Matteo Rizzo
2023-09-15 21:22 ` Kees Cook
2023-09-15 21:57 ` Dave Hansen
2023-10-11 9:17 ` Matteo Rizzo
2023-09-15 10:59 ` [RFC PATCH 12/14] mm/slub: introduce the deallocated_pages sysfs attribute Matteo Rizzo
2023-09-15 21:23 ` Kees Cook
2023-09-15 10:59 ` [RFC PATCH 13/14] mm/slub: sanity-check freepointers Matteo Rizzo
2023-09-15 21:26 ` Kees Cook
2023-09-15 10:59 ` [RFC PATCH 14/14] security: add documentation for SLAB_VIRTUAL Matteo Rizzo
2023-09-15 21:34 ` Kees Cook
2023-09-20 9:04 ` Vlastimil Babka
2023-09-15 15:19 ` [RFC PATCH 00/14] Prevent cross-cache attacks in the SLUB allocator Dave Hansen
2023-09-15 16:30 ` Lameter, Christopher
2023-09-18 12:08 ` Matteo Rizzo
2023-09-18 17:39 ` Ingo Molnar
2023-09-18 18:05 ` Linus Torvalds
2023-09-19 15:48 ` Matteo Rizzo
2023-09-19 16:02 ` Dave Hansen
2023-09-19 17:56 ` Kees Cook
2023-09-19 18:49 ` Linus Torvalds
2023-09-19 13:42 ` Matteo Rizzo
2023-09-19 15:56 ` Dave Hansen
2023-09-20 7:44 ` Ingo Molnar
2023-09-20 8:49 ` Vlastimil Babka
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