linux-mm.kvack.org archive mirror
 help / color / mirror / Atom feed
From: Daniel Axtens <dja@axtens.net>
To: kasan-dev@googlegroups.com, linux-mm@kvack.org, x86@kernel.org,
	aryabinin@virtuozzo.com, glider@google.com, luto@kernel.org,
	linux-kernel@vger.kernel.org, mark.rutland@arm.com,
	dvyukov@google.com, christophe.leroy@c-s.fr
Cc: linuxppc-dev@lists.ozlabs.org, gor@linux.ibm.com,
	Daniel Axtens <dja@axtens.net>
Subject: [PATCH v8 0/5] kasan: support backing vmalloc space with real shadow memory
Date: Tue,  1 Oct 2019 16:58:29 +1000	[thread overview]
Message-ID: <20191001065834.8880-1-dja@axtens.net> (raw)

Currently, vmalloc space is backed by the early shadow page. This
means that kasan is incompatible with VMAP_STACK.

This series provides a mechanism to back vmalloc space with real,
dynamically allocated memory. I have only wired up x86, because that's
the only currently supported arch I can work with easily, but it's
very easy to wire up other architectures, and it appears that there is
some work-in-progress code to do this on arm64 and s390.

This has been discussed before in the context of VMAP_STACK:
 - https://bugzilla.kernel.org/show_bug.cgi?id=202009
 - https://lkml.org/lkml/2018/7/22/198
 - https://lkml.org/lkml/2019/7/19/822

In terms of implementation details:

Most mappings in vmalloc space are small, requiring less than a full
page of shadow space. Allocating a full shadow page per mapping would
therefore be wasteful. Furthermore, to ensure that different mappings
use different shadow pages, mappings would have to be aligned to
KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE.

Instead, share backing space across multiple mappings. Allocate a
backing page when a mapping in vmalloc space uses a particular page of
the shadow region. This page can be shared by other vmalloc mappings
later on.

We hook in to the vmap infrastructure to lazily clean up unused shadow
memory.

v1: https://lore.kernel.org/linux-mm/20190725055503.19507-1-dja@axtens.net/
v2: https://lore.kernel.org/linux-mm/20190729142108.23343-1-dja@axtens.net/
 Address review comments:
 - Patch 1: use kasan_unpoison_shadow's built-in handling of
            ranges that do not align to a full shadow byte
 - Patch 3: prepopulate pgds rather than faulting things in
v3: https://lore.kernel.org/linux-mm/20190731071550.31814-1-dja@axtens.net/
 Address comments from Mark Rutland:
 - kasan_populate_vmalloc is a better name
 - handle concurrency correctly
 - various nits and cleanups
 - relax module alignment in KASAN_VMALLOC case
v4: https://lore.kernel.org/linux-mm/20190815001636.12235-1-dja@axtens.net/
 Changes to patch 1 only:
 - Integrate Mark's rework, thanks Mark!
 - handle the case where kasan_populate_shadow might fail
 - poision shadow on free, allowing the alloc path to just
     unpoision memory that it uses
v5: https://lore.kernel.org/linux-mm/20190830003821.10737-1-dja@axtens.net/
 Address comments from Christophe Leroy:
 - Fix some issues with my descriptions in commit messages and docs
 - Dynamically free unused shadow pages by hooking into the vmap book-keeping
 - Split out the test into a separate patch
 - Optional patch to track the number of pages allocated
 - minor checkpatch cleanups
v6: https://lore.kernel.org/linux-mm/20190902112028.23773-1-dja@axtens.net/
 Properly guard freeing pages in patch 1, drop debugging code.
v7: https://lore.kernel.org/linux-mm/20190903145536.3390-1-dja@axtens.net/
    Add a TLB flush on freeing, thanks Mark Rutland.
    Explain more clearly how I think freeing is concurrency-safe.
v8: rename kasan_vmalloc/shadow_pages to kasan/vmalloc_shadow_pages

Daniel Axtens (5):
  kasan: support backing vmalloc space with real shadow memory
  kasan: add test for vmalloc
  fork: support VMAP_STACK with KASAN_VMALLOC
  x86/kasan: support KASAN_VMALLOC
  kasan debug: track pages allocated for vmalloc shadow

 Documentation/dev-tools/kasan.rst |  63 ++++++++
 arch/Kconfig                      |   9 +-
 arch/x86/Kconfig                  |   1 +
 arch/x86/mm/kasan_init_64.c       |  60 ++++++++
 include/linux/kasan.h             |  31 ++++
 include/linux/moduleloader.h      |   2 +-
 include/linux/vmalloc.h           |  12 ++
 kernel/fork.c                     |   4 +
 lib/Kconfig.kasan                 |  16 +++
 lib/test_kasan.c                  |  26 ++++
 mm/kasan/common.c                 | 230 ++++++++++++++++++++++++++++++
 mm/kasan/generic_report.c         |   3 +
 mm/kasan/kasan.h                  |   1 +
 mm/vmalloc.c                      |  45 +++++-
 14 files changed, 497 insertions(+), 6 deletions(-)

-- 
2.20.1



             reply	other threads:[~2019-10-01  6:58 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-01  6:58 Daniel Axtens [this message]
2019-10-01  6:58 ` [PATCH v8 1/5] kasan: support backing vmalloc space with real shadow memory Daniel Axtens
2019-10-01 10:17   ` Uladzislau Rezki
2019-10-02  1:23     ` Daniel Axtens
2019-10-02  7:13       ` Christophe Leroy
2019-10-02 11:49       ` Uladzislau Rezki
2019-10-07  8:02   ` Uladzislau Rezki
2019-10-11  5:15     ` Daniel Axtens
2019-10-11 19:57   ` Andrey Ryabinin
2019-10-14 13:57     ` Daniel Axtens
2019-10-14 15:27       ` Mark Rutland
2019-10-15  6:32         ` Daniel Axtens
2019-10-15  6:29       ` Daniel Axtens
2019-10-16 12:19       ` Andrey Ryabinin
2019-10-16 13:22         ` Mark Rutland
2019-10-18 10:43           ` Andrey Ryabinin
2019-10-28  7:39             ` Daniel Axtens
2019-10-28  1:26           ` Daniel Axtens
2019-10-14 15:43   ` Mark Rutland
2019-10-15  6:27     ` Daniel Axtens
2019-10-01  6:58 ` [PATCH v8 2/5] kasan: add test for vmalloc Daniel Axtens
2019-10-01  6:58 ` [PATCH v8 3/5] fork: support VMAP_STACK with KASAN_VMALLOC Daniel Axtens
2019-10-01  6:58 ` [PATCH v8 4/5] x86/kasan: support KASAN_VMALLOC Daniel Axtens
2019-10-01  6:58 ` [PATCH v8 5/5] kasan debug: track pages allocated for vmalloc shadow Daniel Axtens

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=20191001065834.8880-1-dja@axtens.net \
    --to=dja@axtens.net \
    --cc=aryabinin@virtuozzo.com \
    --cc=christophe.leroy@c-s.fr \
    --cc=dvyukov@google.com \
    --cc=glider@google.com \
    --cc=gor@linux.ibm.com \
    --cc=kasan-dev@googlegroups.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=luto@kernel.org \
    --cc=mark.rutland@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).