From: Eric Biggers <ebiggers3@gmail.com>
To: Kees Cook <keescook@chromium.org>
Cc: kernel-hardening@lists.openwall.com,
David Windsor <dave@nullcore.net>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [kernel-hardening] [PATCH 22/23] usercopy: split user-controlled slabs to separate caches
Date: Mon, 19 Jun 2017 21:47:21 -0700 [thread overview]
Message-ID: <20170620044721.GE610@zzz.localdomain> (raw)
In-Reply-To: <1497915397-93805-23-git-send-email-keescook@chromium.org>
On Mon, Jun 19, 2017 at 04:36:36PM -0700, Kees Cook wrote:
> From: David Windsor <dave@nullcore.net>
>
> Some userspace APIs (e.g. ipc, seq_file) provide precise control over
> the size of kernel kmallocs, which provides a trivial way to perform
> heap overflow attacks where the attacker must control neighboring
> allocations of a specific size. Instead, move these APIs into their own
> cache so they cannot interfere with standard kmallocs. This is enabled
> with CONFIG_HARDENED_USERCOPY_SPLIT_KMALLOC.
>
> This patch is modified from Brad Spengler/PaX Team's PAX_USERCOPY_SLABS
> code in the last public patch of grsecurity/PaX based on my understanding
> of the code. Changes or omissions from the original code are mine and
> don't reflect the original grsecurity/PaX code.
>
> Signed-off-by: David Windsor <dave@nullcore.net>
> [kees: added SLAB_NO_MERGE flag to allow split of future no-merge Kconfig]
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> fs/seq_file.c | 2 +-
> include/linux/gfp.h | 9 ++++++++-
> include/linux/slab.h | 12 ++++++++++++
> ipc/msgutil.c | 5 +++--
> mm/slab.h | 3 ++-
> mm/slab_common.c | 29 ++++++++++++++++++++++++++++-
> security/Kconfig | 12 ++++++++++++
> 7 files changed, 66 insertions(+), 6 deletions(-)
>
> diff --git a/fs/seq_file.c b/fs/seq_file.c
> index dc7c2be963ed..5caa58a19bdc 100644
> --- a/fs/seq_file.c
> +++ b/fs/seq_file.c
> @@ -25,7 +25,7 @@ static void seq_set_overflow(struct seq_file *m)
>
> static void *seq_buf_alloc(unsigned long size)
> {
> - return kvmalloc(size, GFP_KERNEL);
> + return kvmalloc(size, GFP_KERNEL | GFP_USERCOPY);
> }
>
Also forgot to mention the obvious: there are way more places where GFP_USERCOPY
would need to be (or should be) used. Helper functions like memdup_user() and
memdup_user_nul() would be the obvious ones. And just a random example, some of
the keyrings syscalls (callable with no privileges) do a kmalloc() with
user-controlled contents and size.
So I think this by itself needs its own patch series.
Eric
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next prev parent reply other threads:[~2017-06-20 4:47 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 [this message]
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
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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