From: Rik van Riel <riel@redhat.com>
To: Laura Abbott <labbott@redhat.com>,
Kees Cook <keescook@chromium.org>,
kernel-hardening@lists.openwall.com
Cc: Laura Abbott <labbott@fedoraproject.org>,
Balbir Singh <bsingharora@gmail.com>,
Daniel Micay <danielmicay@gmail.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Casey Schaufler <casey@schaufler-ca.com>,
PaX Team <pageexec@freemail.hu>,
Brad Spengler <spender@grsecurity.net>,
Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Tony Luck <tony.luck@intel.com>,
Fenghua Yu <fenghua.yu@intel.com>,
"David S. Miller" <davem@davemloft.net>,
x86@kernel.org, Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@suse.de>,
Mathias Krause <minipli@googlemail.com>, Jan Kara <jack@suse.cz>,
Vitaly Wool <vitalywool@gmail.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Dmitry Vyukov <dvyukov@google.com>,
linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org,
linux-arch@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: [kernel-hardening] Re: [PATCH v4 12/12] mm: SLUB hardened usercopy support
Date: Mon, 25 Jul 2016 20:22:00 -0400 [thread overview]
Message-ID: <1469492520.30053.123.camel@redhat.com> (raw)
In-Reply-To: <9fca8a3c-da82-d609-79bb-4f5a779cbc1b@redhat.com>
[-- Attachment #1: Type: text/plain, Size: 5346 bytes --]
On Mon, 2016-07-25 at 16:29 -0700, Laura Abbott wrote:
> On 07/25/2016 02:42 PM, Rik van Riel wrote:
> > On Mon, 2016-07-25 at 12:16 -0700, Laura Abbott wrote:
> > > On 07/20/2016 01:27 PM, Kees Cook wrote:
> > > > Under CONFIG_HARDENED_USERCOPY, this adds object size checking
> > > > to
> > > > the
> > > > SLUB allocator to catch any copies that may span objects.
> > > > Includes
> > > > a
> > > > redzone handling fix discovered by Michael Ellerman.
> > > >
> > > > Based on code from PaX and grsecurity.
> > > >
> > > > Signed-off-by: Kees Cook <keescook@chromium.org>
> > > > Tested-by: Michael Ellerman <mpe@ellerman.id.au>
> > > > ---
> > > > init/Kconfig | 1 +
> > > > mm/slub.c | 36 ++++++++++++++++++++++++++++++++++++
> > > > 2 files changed, 37 insertions(+)
> > > >
> > > > diff --git a/init/Kconfig b/init/Kconfig
> > > > index 798c2020ee7c..1c4711819dfd 100644
> > > > --- a/init/Kconfig
> > > > +++ b/init/Kconfig
> > > > @@ -1765,6 +1765,7 @@ config SLAB
> > > >
> > > > config SLUB
> > > > bool "SLUB (Unqueued Allocator)"
> > > > + select HAVE_HARDENED_USERCOPY_ALLOCATOR
> > > > help
> > > > SLUB is a slab allocator that minimizes cache line
> > > > usage
> > > > instead of managing queues of cached objects (SLAB
> > > > approach).
> > > > diff --git a/mm/slub.c b/mm/slub.c
> > > > index 825ff4505336..7dee3d9a5843 100644
> > > > --- a/mm/slub.c
> > > > +++ b/mm/slub.c
> > > > @@ -3614,6 +3614,42 @@ void *__kmalloc_node(size_t size, gfp_t
> > > > flags, int node)
> > > > EXPORT_SYMBOL(__kmalloc_node);
> > > > #endif
> > > >
> > > > +#ifdef CONFIG_HARDENED_USERCOPY
> > > > +/*
> > > > + * Rejects objects that are incorrectly sized.
> > > > + *
> > > > + * Returns NULL if check passes, otherwise const char * to
> > > > name of
> > > > cache
> > > > + * to indicate an error.
> > > > + */
> > > > +const char *__check_heap_object(const void *ptr, unsigned long
> > > > n,
> > > > + struct page *page)
> > > > +{
> > > > + struct kmem_cache *s;
> > > > + unsigned long offset;
> > > > + size_t object_size;
> > > > +
> > > > + /* Find object and usable object size. */
> > > > + s = page->slab_cache;
> > > > + object_size = slab_ksize(s);
> > > > +
> > > > + /* Find offset within object. */
> > > > + offset = (ptr - page_address(page)) % s->size;
> > > > +
> > > > + /* Adjust for redzone and reject if within the
> > > > redzone. */
> > > > + if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE) {
> > > > + if (offset < s->red_left_pad)
> > > > + return s->name;
> > > > + offset -= s->red_left_pad;
> > > > + }
> > > > +
> > > > + /* Allow address range falling entirely within object
> > > > size. */
> > > > + if (offset <= object_size && n <= object_size -
> > > > offset)
> > > > + return NULL;
> > > > +
> > > > + return s->name;
> > > > +}
> > > > +#endif /* CONFIG_HARDENED_USERCOPY */
> > > > +
> > >
> > > I compared this against what check_valid_pointer does for
> > > SLUB_DEBUG
> > > checking. I was hoping we could utilize that function to avoid
> > > duplication but a) __check_heap_object needs to allow accesses
> > > anywhere
> > > in the object, not just the beginning b) accessing page->objects
> > > is racy without the addition of locking in SLUB_DEBUG.
> > >
> > > Still, the ptr < page_address(page) check from
> > > __check_heap_object
> > > would
> > > be good to add to avoid generating garbage large offsets and
> > > trying
> > > to
> > > infer C math.
> > >
> > > diff --git a/mm/slub.c b/mm/slub.c
> > > index 7dee3d9..5370e4f 100644
> > > --- a/mm/slub.c
> > > +++ b/mm/slub.c
> > > @@ -3632,6 +3632,9 @@ const char *__check_heap_object(const void
> > > *ptr, unsigned long n,
> > > s = page->slab_cache;
> > > object_size = slab_ksize(s);
> > >
> > > + if (ptr < page_address(page))
> > > + return s->name;
> > > +
> > > /* Find offset within object. */
> > > offset = (ptr - page_address(page)) % s->size;
> > >
> >
> > I don't get it, isn't that already guaranteed because we
> > look for the page that ptr is in, before __check_heap_object
> > is called?
> >
> > Specifically, in patch 3/12:
> >
> > + page = virt_to_head_page(ptr);
> > +
> > + /* Check slab allocator for flags and size. */
> > + if (PageSlab(page))
> > + return __check_heap_object(ptr, n, page);
> >
> > How can that generate a ptr that is not inside the page?
> >
> > What am I overlooking? And, should it be in the changelog or
> > a comment? :)
> >
>
>
> I ran into the subtraction issue when the vmalloc detection wasn't
> working on ARM64, somehow virt_to_head_page turned into a page
> that happened to have PageSlab set. I agree if everything is working
> properly this is redundant but given the type of feature this is, a
> little bit of redundancy against a system running off into the weeds
> or bad patches might be warranted.
>
That's fair. I have no objection to the check, but would
like to see it documented, since it does look a little out
of place.
--
All Rights Reversed.
[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 473 bytes --]
next prev parent reply other threads:[~2016-07-26 0:22 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-20 20:26 [kernel-hardening] [PATCH v4 00/12] mm: Hardened usercopy Kees Cook
2016-07-20 20:26 ` [kernel-hardening] [PATCH v4 01/12] mm: Add is_migrate_cma_page Kees Cook
2016-07-20 20:26 ` [kernel-hardening] [PATCH v4 02/12] mm: Implement stack frame object validation Kees Cook
2016-07-20 20:26 ` [kernel-hardening] [PATCH v4 03/12] mm: Hardened usercopy Kees Cook
2016-07-20 20:26 ` [kernel-hardening] [PATCH v4 04/12] x86/uaccess: Enable hardened usercopy Kees Cook
2016-07-20 20:27 ` [kernel-hardening] [PATCH v4 05/12] ARM: uaccess: " Kees Cook
2016-07-20 20:27 ` [kernel-hardening] [PATCH v4 06/12] arm64/uaccess: " Kees Cook
2016-07-20 20:27 ` [kernel-hardening] [PATCH v4 07/12] ia64/uaccess: " Kees Cook
2016-07-20 20:27 ` [kernel-hardening] [PATCH v4 08/12] powerpc/uaccess: " Kees Cook
2016-07-20 20:27 ` [kernel-hardening] [PATCH v4 09/12] sparc/uaccess: " Kees Cook
2016-07-20 20:27 ` [kernel-hardening] [PATCH v4 10/12] s390/uaccess: " Kees Cook
2016-07-20 20:27 ` [kernel-hardening] [PATCH v4 11/12] mm: SLAB hardened usercopy support Kees Cook
2016-07-20 20:27 ` [kernel-hardening] [PATCH v4 12/12] mm: SLUB " Kees Cook
2016-07-25 19:16 ` [kernel-hardening] " Laura Abbott
2016-07-25 20:45 ` Kees Cook
2016-07-26 0:54 ` Laura Abbott
2016-07-25 21:42 ` Rik van Riel
2016-07-25 23:29 ` Laura Abbott
2016-07-26 0:22 ` Rik van Riel [this message]
2016-07-23 0:36 ` [kernel-hardening] Re: [PATCH v4 00/12] mm: Hardened usercopy Laura Abbott
2016-07-25 17:50 ` Kees Cook
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1469492520.30053.123.camel@redhat.com \
--to=riel@redhat.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=ard.biesheuvel@linaro.org \
--cc=benh@kernel.crashing.org \
--cc=bp@suse.de \
--cc=bsingharora@gmail.com \
--cc=casey@schaufler-ca.com \
--cc=catalin.marinas@arm.com \
--cc=cl@linux.com \
--cc=danielmicay@gmail.com \
--cc=davem@davemloft.net \
--cc=dvyukov@google.com \
--cc=fenghua.yu@intel.com \
--cc=iamjoonsoo.kim@lge.com \
--cc=jack@suse.cz \
--cc=jpoimboe@redhat.com \
--cc=keescook@chromium.org \
--cc=kernel-hardening@lists.openwall.com \
--cc=labbott@fedoraproject.org \
--cc=labbott@redhat.com \
--cc=linux-arch@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-ia64@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux@armlinux.org.uk \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=luto@kernel.org \
--cc=minipli@googlemail.com \
--cc=mpe@ellerman.id.au \
--cc=pageexec@freemail.hu \
--cc=penberg@kernel.org \
--cc=rientjes@google.com \
--cc=sparclinux@vger.kernel.org \
--cc=spender@grsecurity.net \
--cc=tony.luck@intel.com \
--cc=vitalywool@gmail.com \
--cc=will.deacon@arm.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).