From: Kees Cook <keescook@chromium.org>
To: Daniel Micay <danielmicay@gmail.com>
Cc: "kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
David Windsor <dave@nullcore.net>, Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [kernel-hardening] [PATCH 23/23] mm: Allow slab_nomerge to be set at build time
Date: Tue, 20 Jun 2017 15:51:18 -0700 [thread overview]
Message-ID: <CAGXu5jJckTkYqWRv5AUv=Ks8_477xuZn=RB+0tiXC=sGDe1QEA@mail.gmail.com> (raw)
In-Reply-To: <1497931790.11009.1.camel@gmail.com>
On Mon, Jun 19, 2017 at 9:09 PM, Daniel Micay <danielmicay@gmail.com> wrote:
> On Mon, 2017-06-19 at 16:36 -0700, Kees Cook wrote:
>> Some hardened environments want to build kernels with slab_nomerge
>> already set (so that they do not depend on remembering to set the
>> kernel
>> command line option). This is desired to reduce the risk of kernel
>> heap
>> overflows being able to overwrite objects from merged caches,
>> increasing
>> the difficulty of these attacks. By keeping caches unmerged, these
>> kinds
>> of exploits can usually only damage objects in the same cache (though
>> the
>> risk to metadata exploitation is unchanged).
>
> It also further fragments the ability to influence slab cache layout,
> i.e. primitives to do things like filling up slabs to set things up for
> an exploit might not be able to deal with the target slabs anymore. It
> doesn't need to be mentioned but it's something to think about too. In
> theory, disabling merging can make it *easier* to get the right layout
> too if there was some annoyance that's now split away. It's definitely a
> lot more good than bad for security though, but allocator changes have
> subtle impact on exploitation. This can make caches more deterministic.
Good point about changes to heap grooming; I'll adjust the commit log.
-Kees
--
Kees Cook
Pixel Security
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next prev parent reply other threads:[~2017-06-20 22:51 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-19 23:36 [PATCH 00/23] Hardened usercopy whitelisting Kees Cook
2017-06-19 23:36 ` [PATCH 01/23] usercopy: Prepare for " Kees Cook
2017-06-19 23:36 ` [PATCH 02/23] usercopy: Enforce slab cache usercopy region boundaries Kees Cook
2017-06-19 23:36 ` [PATCH 03/23] vfs: define usercopy region in names_cache slab caches Kees Cook
2017-06-19 23:36 ` [PATCH 04/23] vfs: copy struct mount.mnt_id to userspace using put_user() Kees Cook
2017-06-19 23:36 ` [PATCH 05/23] befs: define usercopy region in befs_inode_cache slab cache Kees Cook
2017-06-19 23:36 ` [PATCH 06/23] cifs: define usercopy region in cifs_request " Kees Cook
2017-06-19 23:36 ` [PATCH 07/23] exofs: define usercopy region in exofs_inode_cache " Kees Cook
2017-06-19 23:36 ` [PATCH 08/23] ext2: define usercopy region in ext2_inode_cache " Kees Cook
2017-06-19 23:36 ` [PATCH 09/23] ext4: define usercopy region in ext4_inode_cache " Kees Cook
2017-06-19 23:36 ` [PATCH 10/23] vxfs: define usercopy region in vxfs_inode " Kees Cook
2017-06-19 23:36 ` [PATCH 11/23] jfs: define usercopy region in jfs_ip " Kees Cook
2017-06-19 23:36 ` [PATCH 12/23] orangefs: define usercopy region in orangefs_inode_cache " Kees Cook
2017-06-19 23:36 ` [PATCH 13/23] ufs: define usercopy region in ufs_inode_cache " Kees Cook
2017-06-19 23:36 ` [PATCH 14/23] fork: define usercopy region in thread_stack, task_struct, mm_struct slab caches Kees Cook
2017-06-19 23:36 ` [PATCH 15/23] net: define usercopy region in struct proto slab cache Kees Cook
2017-06-19 23:36 ` [PATCH 16/23] net: copy struct sctp_sock.autoclose to userspace using put_user() Kees Cook
2017-06-19 23:36 ` [PATCH 17/23] dcache: define usercopy region in dentry_cache slab cache Kees Cook
2017-06-20 4:08 ` [kernel-hardening] " Eric Biggers
2017-06-28 16:44 ` Kees Cook
2017-06-28 16:55 ` Eric Biggers
2017-06-19 23:36 ` [PATCH 18/23] scsi: define usercopy region in scsi_sense_cache " Kees Cook
2017-06-19 23:36 ` [PATCH 19/23] xfs: define usercopy region in xfs_inode " Kees Cook
2017-06-19 23:36 ` [PATCH 20/23] usercopy: convert kmalloc caches to usercopy caches Kees Cook
2017-06-19 23:36 ` [PATCH 21/23] usercopy: Restrict non-usercopy caches to size 0 Kees Cook
2017-06-20 4:04 ` [kernel-hardening] " Eric Biggers
2017-06-28 17:03 ` Kees Cook
2017-06-19 23:36 ` [PATCH 22/23] usercopy: split user-controlled slabs to separate caches Kees Cook
2017-06-20 4:24 ` [kernel-hardening] " Eric Biggers
2017-06-20 4:47 ` Eric Biggers
2017-06-20 22:27 ` Kees Cook
2017-06-20 20:24 ` Laura Abbott
2017-06-20 22:22 ` Kees Cook
2017-06-27 7:31 ` Michal Hocko
2017-06-27 22:07 ` Kees Cook
2017-06-28 8:54 ` Michal Hocko
2017-06-19 23:36 ` [PATCH 23/23] mm: Allow slab_nomerge to be set at build time Kees Cook
2017-06-20 4:09 ` [kernel-hardening] " Daniel Micay
2017-06-20 22:51 ` Kees Cook [this message]
2017-06-20 4:29 ` Eric Biggers
2017-06-20 23:09 ` Kees Cook
2017-06-20 19:41 ` [kernel-hardening] [PATCH 00/23] Hardened usercopy whitelisting Rik van Riel
2017-10-20 22:40 ` Paolo Bonzini
2017-10-20 23:25 ` Paolo Bonzini
2017-10-21 3:04 ` Kees Cook
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