1. 24 Nov, 2020 8 commits
  2. 14 Oct, 2020 1 commit
  3. 07 Aug, 2020 2 commits
  4. 09 Jun, 2020 2 commits
    • Mike Rapoport's avatar
      mm: reorder includes after introduction of linux/pgtable.h · 65fddcfc
      Mike Rapoport authored
      
      
      The replacement of <asm/pgrable.h> with <linux/pgtable.h> made the include
      of the latter in the middle of asm includes.  Fix this up with the aid of
      the below script and manual adjustments here and there.
      
      	import sys
      	import re
      
      	if len(sys.argv) is not 3:
      	    print "USAGE: %s <file> <header>" % (sys.argv[0])
      	    sys.exit(1)
      
      	hdr_to_move="#include <linux/%s>" % sys.argv[2]
      	moved = False
      	in_hdrs = False
      
      	with open(sys.argv[1], "r") as f:
      	    lines = f.readlines()
      	    for _line in lines:
      		line = _line.rstrip('
      ')
      		if line == hdr_to_move:
      		    continue
      		if line.startswith("#include <linux/"):
      		    in_hdrs = True
      		elif not moved and in_hdrs:
      		    moved = True
      		    print hdr_to_move
      		print line
      Signed-off-by: default avatarMike Rapoport <rppt@linux.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Cain <bcain@codeaurora.org>
      Cc: Catalin Marinas <catalin.marinas@arm.com>
      Cc: Chris Zankel <chris@zankel.net>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>
      Cc: Greentime Hu <green.hu@gmail.com>
      Cc: Greg Ungerer <gerg@linux-m68k.org>
      Cc: Guan Xuetao <gxt@pku.edu.cn>
      Cc: Guo Ren <guoren@kernel.org>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Helge Deller <deller@gmx.de>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Ley Foon Tan <ley.foon.tan@intel.com>
      Cc: Mark Salter <msalter@redhat.com>
      Cc: Matthew Wilcox <willy@infradead.org>
      Cc: Matt Turner <mattst88@gmail.com>
      Cc: Max Filippov <jcmvbkbc@gmail.com>
      Cc: Michael Ellerman <mpe@ellerman.id.au>
      Cc: Michal Simek <monstr@monstr.eu>
      Cc: Nick Hu <nickhu@andestech.com>
      Cc: Paul Walmsley <paul.walmsley@sifive.com>
      Cc: Richard Weinberger <richard@nod.at>
      Cc: Rich Felker <dalias@libc.org>
      Cc: Russell King <linux@armlinux.org.uk>
      Cc: Stafford Horne <shorne@gmail.com>
      Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Tony Luck <tony.luck@intel.com>
      Cc: Vincent Chen <deanbo422@gmail.com>
      Cc: Vineet Gupta <vgupta@synopsys.com>
      Cc: Will Deacon <will@kernel.org>
      Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
      Link: http://lkml.kernel.org/r/20200514170327.31389-4-rppt@kernel.org
      
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      65fddcfc
    • Mike Rapoport's avatar
      mm: introduce include/linux/pgtable.h · ca5999fd
      Mike Rapoport authored
      
      
      The include/linux/pgtable.h is going to be the home of generic page table
      manipulation functions.
      
      Start with moving asm-generic/pgtable.h to include/linux/pgtable.h and
      make the latter include asm/pgtable.h.
      Signed-off-by: default avatarMike Rapoport <rppt@linux.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Cain <bcain@codeaurora.org>
      Cc: Catalin Marinas <catalin.marinas@arm.com>
      Cc: Chris Zankel <chris@zankel.net>
      Cc: "David S. Miller" <davem@davemloft.net>
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>
      Cc: Greentime Hu <green.hu@gmail.com>
      Cc: Greg Ungerer <gerg@linux-m68k.org>
      Cc: Guan Xuetao <gxt@pku.edu.cn>
      Cc: Guo Ren <guoren@kernel.org>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Helge Deller <deller@gmx.de>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Ley Foon Tan <ley.foon.tan@intel.com>
      Cc: Mark Salter <msalter@redhat.com>
      Cc: Matthew Wilcox <willy@infradead.org>
      Cc: Matt Turner <mattst88@gmail.com>
      Cc: Max Filippov <jcmvbkbc@gmail.com>
      Cc: Michael Ellerman <mpe@ellerman.id.au>
      Cc: Michal Simek <monstr@monstr.eu>
      Cc: Nick Hu <nickhu@andestech.com>
      Cc: Paul Walmsley <paul.walmsley@sifive.com>
      Cc: Richard Weinberger <richard@nod.at>
      Cc: Rich Felker <dalias@libc.org>
      Cc: Russell King <linux@armlinux.org.uk>
      Cc: Stafford Horne <shorne@gmail.com>
      Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Tony Luck <tony.luck@intel.com>
      Cc: Vincent Chen <deanbo422@gmail.com>
      Cc: Vineet Gupta <vgupta@synopsys.com>
      Cc: Will Deacon <will@kernel.org>
      Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
      Link: http://lkml.kernel.org/r/20200514170327.31389-3-rppt@kernel.org
      
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      ca5999fd
  5. 02 Apr, 2020 1 commit
  6. 31 Dec, 2019 1 commit
    • Jann Horn's avatar
      x86/kasan: Print original address on #GP · 2f004eea
      Jann Horn authored
      
      
      Make #GP exceptions caused by out-of-bounds KASAN shadow accesses easier
      to understand by computing the address of the original access and
      printing that. More details are in the comments in the patch.
      
      This turns an error like this:
      
        kasan: CONFIG_KASAN_INLINE enabled
        kasan: GPF could be caused by NULL-ptr deref or user memory access
        general protection fault, probably for non-canonical address
            0xe017577ddf75b7dd: 0000 [#1] PREEMPT SMP KASAN PTI
      
      into this:
      
        general protection fault, probably for non-canonical address
            0xe017577ddf75b7dd: 0000 [#1] PREEMPT SMP KASAN PTI
        KASAN: maybe wild-memory-access in range
            [0x00badbeefbadbee8-0x00badbeefbadbeef]
      
      The hook is placed in architecture-independent code, but is currently
      only wired up to the X86 exception handler because I'm not sufficiently
      familiar with the address space layout and exception handling mechanisms
      on other architectures.
      Signed-off-by: default avatarJann Horn <jannh@google.com>
      Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
      Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
      Cc: Alexander Potapenko <glider@google.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andrey Konovalov <andreyknvl@google.com>
      Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
      Cc: Andy Lutomirski <luto@kernel.org>
      Cc: Dave Hansen <dave.hansen@linux.intel.com>
      Cc: "H. Peter Anvin" <hpa@zytor.com>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: kasan-dev@googlegroups.com
      Cc: linux-mm <linux-mm@kvack.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Sean Christopherson <sean.j.christopherson@intel.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: x86-ml <x86@kernel.org>
      Link: https://lkml.kernel.org/r/20191218231150.12139-4-jannh@google.com
      2f004eea
  7. 18 Dec, 2019 1 commit
  8. 01 Dec, 2019 1 commit
    • Daniel Axtens's avatar
      kasan: support backing vmalloc space with real shadow memory · 3c5c3cfb
      Daniel Axtens authored
      Patch series "kasan: support backing vmalloc space with real shadow
      memory", v11.
      
      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.
      
      Testing with test_vmalloc.sh on an x86 VM with 2 vCPUs shows that:
      
       - Turning on KASAN, inline instrumentation, without vmalloc, introuduces
         a 4.1x-4.2x slowdown in vmalloc operations.
      
       - Turning this on introduces the following slowdowns over KASAN:
           * ~1.76x slower single-threaded (test_vmalloc.sh performance)
           * ~2.18x slower when both cpus are performing operations
             simultaneously (test_vmalloc.sh sequential_test_order=1)
      
      This is unfortunate but given that this is a debug feature only, not the
      end of the world.  The benchmarks are also a stress-test for the vmalloc
      subsystem: they're not indicative of an overall 2x slowdown!
      
      This patch (of 4):
      
      Hook into vmalloc and vmap, and dynamically allocate real shadow memory
      to back the mappings.
      
      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.
      
      To avoid the difficulties around swapping mappings around, this code
      expects that the part of the shadow region that covers the vmalloc space
      will not be covered by the early shadow page, but will be left unmapped.
      This will require changes in arch-specific code.
      
      This allows KASAN with VMAP_STACK, and may be helpful for architectures
      that do not have a separate module space (e.g.  powerpc64, which I am
      currently working on).  It also allows relaxing the module alignment
      back to PAGE_SIZE.
      
      Testing with test_vmalloc.sh on an x86 VM with 2 vCPUs shows that:
      
       - Turning on KASAN, inline instrumentation, without vmalloc, introuduces
         a 4.1x-4.2x slowdown in vmalloc operations.
      
       - Turning this on introduces the following slowdowns over KASAN:
           * ~1.76x slower single-threaded (test_vmalloc.sh performance)
           * ~2.18x slower when both cpus are performing operations
             simultaneously (test_vmalloc.sh sequential_test_order=3D1)
      
      This is unfortunate but given that this is a debug feature only, not the
      end of the world.
      
      The full benchmark results are:
      
      Performance
      
                                    No KASAN      KASAN original x baseline  KASAN vmalloc x baseline    x KASAN
      
      fix_size_alloc_test             662004            11404956      17.23       19144610      28.92       1.68
      full_fit_alloc_test             710950            12029752      16.92       13184651      18.55       1.10
      long_busy_list_alloc_test      9431875            43990172       4.66       82970178       8.80       1.89
      random_size_alloc_test         5033626            23061762       4.58       47158834       9.37       2.04
      fix_align_alloc_test           1252514            15276910      12.20       31266116      24.96       2.05
      random_size_align_alloc_te     1648501            14578321       8.84       25560052      15.51       1.75
      align_shift_alloc_test             147                 830       5.65           5692      38.72       6.86
      pcpu_alloc_test                  80732              125520       1.55         140864       1.74       1.12
      Total Cycles              119240774314        763211341128       6.40  1390338696894      11.66       1.82
      
      Sequential, 2 cpus
      
                                    No KASAN      KASAN original x baseline  KASAN vmalloc x baseline    x KASAN
      
      fix_size_alloc_test            1423150            14276550      10.03       27733022      19.49       1.94
      full_fit_alloc_test            1754219            14722640       8.39       15030786       8.57       1.02
      long_busy_list_alloc_test     11451858            52154973       4.55      107016027       9.34       2.05
      random_size_alloc_test         5989020            26735276       4.46       68885923      11.50       2.58
      fix_align_alloc_test           2050976            20166900       9.83       50491675      24.62       2.50
      random_size_align_alloc_te     2858229            17971700       6.29       38730225      13.55       2.16
      align_shift_alloc_test             405                6428      15.87          26253      64.82       4.08
      pcpu_alloc_test                 127183              151464       1.19         216263       1.70       1.43
      Total Cycles               54181269392        308723699764       5.70   650772566394      12.01       2.11
      fix_size_alloc_test            1420404            14289308      10.06       27790035      19.56       1.94
      full_fit_alloc_test            1736145            14806234       8.53       15274301       8.80       1.03
      long_busy_list_alloc_test     11404638            52270785       4.58      107550254       9.43       2.06
      random_size_alloc_test         6017006            26650625       4.43       68696127      11.42       2.58
      fix_align_alloc_test           2045504            20280985       9.91       50414862      24.65       2.49
      random_size_align_alloc_te     2845338            17931018       6.30       38510276      13.53       2.15
      align_shift_alloc_test             472                3760       7.97           9656      20.46       2.57
      pcpu_alloc_test                 118643              132732       1.12         146504       1.23       1.10
      Total Cycles               54040011688        309102805492       5.72   651325675652      12.05       2.11
      
      [dja@axtens.net: fixups]
        Link: http://lkml.kernel.org/r/20191120052719.7201-1-dja@axtens.net
      Link: https://bugzilla.kernel.org/show_bug.cgi?id=3D202009
      Link: http://lkml.kernel.org/r/20191031093909.9228-2-dja@axtens.net
      
      
      Signed-off-by: Mark Rutland <mark.rutland@arm.com> [shadow rework]
      Signed-off-by: default avatarDaniel Axtens <dja@axtens.net>
      Co-developed-by: Mark Rutland's avatarMark Rutland <mark.rutland@arm.com>
      Acked-by: default avatarVasily Gorbik <gor@linux.ibm.com>
      Reviewed-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
      Cc: Alexander Potapenko <glider@google.com>
      Cc: Dmitry Vyukov <dvyukov@google.com>
      Cc: Christophe Leroy <christophe.leroy@c-s.fr>
      Cc: Qian Cai <cai@lca.pw>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      3c5c3cfb
  9. 12 Jul, 2019 1 commit
  10. 28 Dec, 2018 7 commits
    • Andrey Konovalov's avatar
      kasan: add __must_check annotations to kasan hooks · 66afc7f1
      Andrey Konovalov authored
      This patch adds __must_check annotations to kasan hooks that return a
      pointer to make sure that a tagged pointer always gets propagated.
      
      Link: http://lkml.kernel.org/r/03b269c5e453945f724bfca3159d4e1333a8fb1c.1544099024.git.andreyknvl@google.com
      
      Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
      Suggested-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Dmitry Vyukov <dvyukov@google.com>
      Cc: Mark Rutland <mark.rutland@arm.com>
      Cc: Will Deacon <will.deacon@arm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      66afc7f1
    • Andrey Konovalov's avatar
      kasan, arm64: add brk handler for inline instrumentation · 41eea9cd
      Andrey Konovalov authored
      Tag-based KASAN inline instrumentation mode (which embeds checks of shadow
      memory into the generated code, instead of inserting a callback) generates
      a brk instruction when a tag mismatch is detected.
      
      This commit adds a tag-based KASAN specific brk handler, that decodes the
      immediate value passed to the brk instructions (to extract information
      about the memory access that triggered the mismatch), reads the register
      values (x0 contains the guilty address) and reports the bug.
      
      Link: http://lkml.kernel.org/r/c91fe7684070e34dc34b419e6b69498f4dcacc2d.1544099024.git.andreyknvl@google.com
      
      Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
      Reviewed-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
      Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
      Acked-by: default avatarWill Deacon <will.deacon@arm.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Mark Rutland <mark.rutland@arm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      41eea9cd
    • Andrey Konovalov's avatar
      kasan: add tag related helper functions · 3c9e3aa1
      Andrey Konovalov authored
      This commit adds a few helper functions, that are meant to be used to work
      with tags embedded in the top byte of kernel pointers: to set, to get or
      to reset the top byte.
      
      Link: http://lkml.kernel.org/r/f6c6437bb8e143bc44f42c3c259c62e734be7935.1544099024.git.andreyknvl@google.com
      
      Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
      Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Dmitry Vyukov <dvyukov@google.com>
      Cc: Mark Rutland <mark.rutland@arm.com>
      Cc: Will Deacon <will.deacon@arm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      3c9e3aa1
    • Andrey Konovalov's avatar
      kasan: initialize shadow to 0xff for tag-based mode · 080eb83f
      Andrey Konovalov authored
      A tag-based KASAN shadow memory cell contains a memory tag, that
      corresponds to the tag in the top byte of the pointer, that points to that
      memory.  The native top byte value of kernel pointers is 0xff, so with
      tag-based KASAN we need to initialize shadow memory to 0xff.
      
      [cai@lca.pw: arm64: skip kmemleak for KASAN again\
        Link: http://lkml.kernel.org/r/20181226020550.63712-1-cai@lca.pw
      Link: http://lkml.kernel.org/r/5cc1b789aad7c99cf4f3ec5b328b147ad53edb40.1544099024.git.andreyknvl@google.com
      
      Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
      Reviewed-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
      Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Mark Rutland <mark.rutland@arm.com>
      Cc: Will Deacon <will.deacon@arm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      080eb83f
    • Andrey Konovalov's avatar
      kasan: rename kasan_zero_page to kasan_early_shadow_page · 9577dd74
      Andrey Konovalov authored
      With tag based KASAN mode the early shadow value is 0xff and not 0x00, so
      this patch renames kasan_zero_(page|pte|pmd|pud|p4d) to
      kasan_early_shadow_(page|pte|pmd|pud|p4d) to avoid confusion.
      
      Link: http://lkml.kernel.org/r/3fed313280ebf4f88645f5b89ccbc066d320e177.1544099024.git.andreyknvl@google.com
      
      Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
      Suggested-by: Mark Rutland's avatarMark Rutland <mark.rutland@arm.com>
      Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Dmitry Vyukov <dvyukov@google.com>
      Cc: Will Deacon <will.deacon@arm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      9577dd74
    • Andrey Konovalov's avatar
      kasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS · 2bd926b4
      Andrey Konovalov authored
      This commit splits the current CONFIG_KASAN config option into two:
      1. CONFIG_KASAN_GENERIC, that enables the generic KASAN mode (the one
         that exists now);
      2. CONFIG_KASAN_SW_TAGS, that enables the software tag-based KASAN mode.
      
      The name CONFIG_KASAN_SW_TAGS is chosen as in the future we will have
      another hardware tag-based KASAN mode, that will rely on hardware memory
      tagging support in arm64.
      
      With CONFIG_KASAN_SW_TAGS enabled, compiler options are changed to
      instrument kernel files with -fsantize=kernel-hwaddress (except the ones
      for which KASAN_SANITIZE := n is set).
      
      Both CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS support both
      CONFIG_KASAN_INLINE and CONFIG_KASAN_OUTLINE instrumentation modes.
      
      This commit also adds empty placeholder (for now) implementation of
      tag-based KASAN specific hooks inserted by the compiler and adjusts
      common hooks implementation.
      
      While this commit adds the CONFIG_KASAN_SW_TAGS config option, this option
      is not selectable, as it depends on HAVE_ARCH_KASAN_SW_TAGS, which we will
      enable once all the infrastracture code has been added.
      
      Link: http://lkml.kernel.org/r/b2550106eb8a68b10fefbabce820910b115aa853.1544099024.git.andreyknvl@google.com
      
      Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
      Reviewed-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
      Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Mark Rutland <mark.rutland@arm.com>
      Cc: Will Deacon <will.deacon@arm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      2bd926b4
    • Andrey Konovalov's avatar
      kasan, mm: change hooks signatures · 0116523c
      Andrey Konovalov authored
      Patch series "kasan: add software tag-based mode for arm64", v13.
      
      This patchset adds a new software tag-based mode to KASAN [1].  (Initially
      this mode was called KHWASAN, but it got renamed, see the naming rationale
      at the end of this section).
      
      The plan is to implement HWASan [2] for the kernel with the incentive,
      that it's going to have comparable to KASAN performance, but in the same
      time consume much less memory, trading that off for somewhat imprecise bug
      detection and being supported only for arm64.
      
      The underlying ideas of the approach used by software tag-based KASAN are:
      
      1. By using the Top Byte Ignore (TBI) arm64 CPU feature, we can store
         pointer tags in the top byte of each kernel pointer.
      
      2. Using shadow memory, we can store memory tags for each chunk of kernel
         memory.
      
      3. On each memory allocation, we can generate a random tag, embed it into
         the returned pointer and set the memory tags that correspond to this
         chunk of memory to the same value.
      
      4. By using compiler instrumentation, before each memory access we can add
         a check that the pointer tag matches the tag of the memory that is being
         accessed.
      
      5. On a tag mismatch we report an error.
      
      With this patchset the existing KASAN mode gets renamed to generic KASAN,
      with the word "generic" meaning that the implementation can be supported
      by any architecture as it is purely software.
      
      The new mode this patchset adds is called software tag-based KASAN.  The
      word "tag-based" refers to the fact that this mode uses tags embedded into
      the top byte of kernel pointers and the TBI arm64 CPU feature that allows
      to dereference such pointers.  The word "software" here means that shadow
      memory manipulation and tag checking on pointer dereference is done in
      software.  As it is the only tag-based implementation right now, "software
      tag-based" KASAN is sometimes referred to as simply "tag-based" in this
      patchset.
      
      A potential expansion of this mode is a hardware tag-based mode, which
      would use hardware memory tagging support (announced by Arm [3]) instead
      of compiler instrumentation and manual shadow memory manipulation.
      
      Same as generic KASAN, software tag-based KASAN is strictly a debugging
      feature.
      
      [1] https://www.kernel.org/doc/html/latest/dev-tools/kasan.html
      
      [2] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html
      
      [3] https://community.arm.com/processors/b/blog/posts/arm-a-profile-architecture-2018-developments-armv85a
      
      ====== Rationale
      
      On mobile devices generic KASAN's memory usage is significant problem.
      One of the main reasons to have tag-based KASAN is to be able to perform a
      similar set of checks as the generic one does, but with lower memory
      requirements.
      
      Comment from Vishwath Mohan <vishwath@google.com>:
      
      I don't have data on-hand, but anecdotally both ASAN and KASAN have proven
      problematic to enable for environments that don't tolerate the increased
      memory pressure well.  This includes
      
      (a) Low-memory form factors - Wear, TV, Things, lower-tier phones like Go,
      (c) Connected components like Pixel's visual core [1].
      
      These are both places I'd love to have a low(er) memory footprint option at
      my disposal.
      
      Comment from Evgenii Stepanov <eugenis@google.com>:
      
      Looking at a live Android device under load, slab (according to
      /proc/meminfo) + kernel stack take 8-10% available RAM (~350MB).  KASAN's
      overhead of 2x - 3x on top of it is not insignificant.
      
      Not having this overhead enables near-production use - ex.  running
      KASAN/KHWASAN kernel on a personal, daily-use device to catch bugs that do
      not reproduce in test configuration.  These are the ones that often cost
      the most engineering time to track down.
      
      CPU overhead is bad, but generally tolerable.  RAM is critical, in our
      experience.  Once it gets low enough, OOM-killer makes your life
      miserable.
      
      [1] https://www.blog.google/products/pixel/pixel-visual-core-image-processing-and-machine-learning-pixel-2/
      
      ====== Technical details
      
      Software tag-based KASAN mode is implemented in a very similar way to the
      generic one. This patchset essentially does the following:
      
      1. TCR_TBI1 is set to enable Top Byte Ignore.
      
      2. Shadow memory is used (with a different scale, 1:16, so each shadow
         byte corresponds to 16 bytes of kernel memory) to store memory tags.
      
      3. All slab objects are aligned to shadow scale, which is 16 bytes.
      
      4. All pointers returned from the slab allocator are tagged with a random
         tag and the corresponding shadow memory is poisoned with the same value.
      
      5. Compiler instrumentation is used to insert tag checks. Either by
         calling callbacks or by inlining them (CONFIG_KASAN_OUTLINE and
         CONFIG_KASAN_INLINE flags are reused).
      
      6. When a tag mismatch is detected in callback instrumentation mode
         KASAN simply prints a bug report. In case of inline instrumentation,
         clang inserts a brk instruction, and KASAN has it's own brk handler,
         which reports the bug.
      
      7. The memory in between slab objects is marked with a reserved tag, and
         acts as a redzone.
      
      8. When a slab object is freed it's marked with a reserved tag.
      
      Bug detection is imprecise for two reasons:
      
      1. We won't catch some small out-of-bounds accesses, that fall into the
         same shadow cell, as the last byte of a slab object.
      
      2. We only have 1 byte to store tags, which means we have a 1/256
         probability of a tag match for an incorrect access (actually even
         slightly less due to reserved tag values).
      
      Despite that there's a particular type of bugs that tag-based KASAN can
      detect compared to generic KASAN: use-after-free after the object has been
      allocated by someone else.
      
      ====== Testing
      
      Some kernel developers voiced a concern that changing the top byte of
      kernel pointers may lead to subtle bugs that are difficult to discover.
      To address this concern deliberate testing has been performed.
      
      It doesn't seem feasible to do some kind of static checking to find
      potential issues with pointer tagging, so a dynamic approach was taken.
      All pointer comparisons/subtractions have been instrumented in an LLVM
      compiler pass and a kernel module that would print a bug report whenever
      two pointers with different tags are being compared/subtracted (ignoring
      comparisons with NULL pointers and with pointers obtained by casting an
      error code to a pointer type) has been used.  Then the kernel has been
      booted in QEMU and on an Odroid C2 board and syzkaller has been run.
      
      This yielded the following results.
      
      The two places that look interesting are:
      
      is_vmalloc_addr in include/linux/mm.h
      is_kernel_rodata in mm/util.c
      
      Here we compare a pointer with some fixed untagged values to make sure
      that the pointer lies in a particular part of the kernel address space.
      Since tag-based KASAN doesn't add tags to pointers that belong to rodata
      or vmalloc regions, this should work as is.  To make sure debug checks to
      those two functions that check that the result doesn't change whether we
      operate on pointers with or without untagging has been added.
      
      A few other cases that don't look that interesting:
      
      Comparing pointers to achieve unique sorting order of pointee objects
      (e.g. sorting locks addresses before performing a double lock):
      
      tty_ldisc_lock_pair_timeout in drivers/tty/tty_ldisc.c
      pipe_double_lock in fs/pipe.c
      unix_state_double_lock in net/unix/af_unix.c
      lock_two_nondirectories in fs/inode.c
      mutex_lock_double in kernel/events/core.c
      
      ep_cmp_ffd in fs/eventpoll.c
      fsnotify_compare_groups fs/notify/mark.c
      
      Nothing needs to be done here, since the tags embedded into pointers
      don't change, so the sorting order would still be unique.
      
      Checks that a pointer belongs to some particular allocation:
      
      is_sibling_entry in lib/radix-tree.c
      object_is_on_stack in include/linux/sched/task_stack.h
      
      Nothing needs to be done here either, since two pointers can only belong
      to the same allocation if they have the same tag.
      
      Overall, since the kernel boots and works, there are no critical bugs.
      As for the rest, the traditional kernel testing way (use until fails) is
      the only one that looks feasible.
      
      Another point here is that tag-based KASAN is available under a separate
      config option that needs to be deliberately enabled. Even though it might
      be used in a "near-production" environment to find bugs that are not found
      during fuzzing or running tests, it is still a debug tool.
      
      ====== Benchmarks
      
      The following numbers were collected on Odroid C2 board. Both generic and
      tag-based KASAN were used in inline instrumentation mode.
      
      Boot time [1]:
      * ~1.7 sec for clean kernel
      * ~5.0 sec for generic KASAN
      * ~5.0 sec for tag-based KASAN
      
      Network performance [2]:
      * 8.33 Gbits/sec for clean kernel
      * 3.17 Gbits/sec for generic KASAN
      * 2.85 Gbits/sec for tag-based KASAN
      
      Slab memory usage after boot [3]:
      * ~40 kb for clean kernel
      * ~105 kb (~260% overhead) for generic KASAN
      * ~47 kb (~20% overhead) for tag-based KASAN
      
      KASAN memory overhead consists of three main parts:
      1. Increased slab memory usage due to redzones.
      2. Shadow memory (the whole reserved once during boot).
      3. Quaratine (grows gradually until some preset limit; the more the limit,
         the more the chance to detect a use-after-free).
      
      Comparing tag-based vs generic KASAN for each of these points:
      1. 20% vs 260% overhead.
      2. 1/16th vs 1/8th of physical memory.
      3. Tag-based KASAN doesn't require quarantine.
      
      [1] Time before the ext4 driver is initialized.
      [2] Measured as `iperf -s & iperf -c 127.0.0.1 -t 30`.
      [3] Measured as `cat /proc/meminfo | grep Slab`.
      
      ====== Some notes
      
      A few notes:
      
      1. The patchset can be found here:
         https://github.com/xairy/kasan-prototype/tree/khwasan
      
      2. Building requires a recent Clang version (7.0.0 or later).
      
      3. Stack instrumentation is not supported yet and will be added later.
      
      This patch (of 25):
      
      Tag-based KASAN changes the value of the top byte of pointers returned
      from the kernel allocation functions (such as kmalloc).  This patch
      updates KASAN hooks signatures and their usage in SLAB and SLUB code to
      reflect that.
      
      Link: http://lkml.kernel.org/r/aec2b5e3973781ff8a6bb6760f8543643202c451.1544099024.git.andreyknvl@google.com
      
      Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
      Reviewed-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
      Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Mark Rutland <mark.rutland@arm.com>
      Cc: Will Deacon <will.deacon@arm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      0116523c
  11. 17 Aug, 2018 1 commit
    • Andrey Ryabinin's avatar
      kernel/memremap, kasan: make ZONE_DEVICE with work with KASAN · 0207df4f
      Andrey Ryabinin authored
      KASAN learns about hotadded memory via the memory hotplug notifier.
      devm_memremap_pages() intentionally skips calling memory hotplug
      notifiers.  So KASAN doesn't know anything about new memory added by
      devm_memremap_pages().  This causes a crash when KASAN tries to access
      non-existent shadow memory:
      
       BUG: unable to handle kernel paging request at ffffed0078000000
       RIP: 0010:check_memory_region+0x82/0x1e0
       Call Trace:
        memcpy+0x1f/0x50
        pmem_do_bvec+0x163/0x720
        pmem_make_request+0x305/0xac0
        generic_make_request+0x54f/0xcf0
        submit_bio+0x9c/0x370
        submit_bh_wbc+0x4c7/0x700
        block_read_full_page+0x5ef/0x870
        do_read_cache_page+0x2b8/0xb30
        read_dev_sector+0xbd/0x3f0
        read_lba.isra.0+0x277/0x670
        efi_partition+0x41a/0x18f0
        check_partition+0x30d/0x5e9
        rescan_partitions+0x18c/0x840
        __blkdev_get+0x859/0x1060
        blkdev_get+0x23f/0x810
        __device_add_disk+0x9c8/0xde0
        pmem_attach_disk+0x9a8/0xf50
        nvdimm_bus_probe+0xf3/0x3c0
        driver_probe_device+0x493/0xbd0
        bus_for_each_drv+0x118/0x1b0
        __device_attach+0x1cd/0x2b0
        bus_probe_device+0x1ac/0x260
        device_add+0x90d/0x1380
        nd_async_device_register+0xe/0x50
        async_run_entry_fn+0xc3/0x5d0
        process_one_work+0xa0a/0x1810
        worker_thread+0x87/0xe80
        kthread+0x2d7/0x390
        ret_from_fork+0x3a/0x50
      
      Add kasan_add_zero_shadow()/kasan_remove_zero_shadow() - post mm_init()
      interface to map/unmap kasan_zero_page at requested virtual addresses.
      And use it to add/remove the shadow memory for hotplugged/unplugged
      device memory.
      
      Link: http://lkml.kernel.org/r/20180629164932.740-1-aryabinin@virtuozzo.com
      Fixes: 41e94a85
      
       ("add devm_memremap_pages")
      Signed-off-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
      Reported-by: default avatarDave Chinner <david@fromorbit.com>
      Reviewed-by: default avatarDan Williams <dan.j.williams@intel.com>
      Tested-by: default avatarDan Williams <dan.j.williams@intel.com>
      Cc: Dmitry Vyukov <dvyukov@google.com>
      Cc: Alexander Potapenko <glider@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      0207df4f
  12. 06 Apr, 2018 1 commit
  13. 14 Feb, 2018 1 commit
  14. 07 Feb, 2018 4 commits
  15. 16 Nov, 2017 1 commit
  16. 02 Nov, 2017 1 commit
    • Greg Kroah-Hartman's avatar
      License cleanup: add SPDX GPL-2.0 license identifier to files with no license · b2441318
      Greg Kroah-Hartman authored
      
      
      Many source files in the tree are missing licensing information, which
      makes it harder for compliance tools to determine the correct license.
      
      By default all files without license information are under the default
      license of the kernel, which is GPL version 2.
      
      Update the files which contain no license information with the 'GPL-2.0'
      SPDX license identifier.  The SPDX identifier is a legally binding
      shorthand, which can be used instead of the full boiler plate text.
      
      This patch is based on work done by Thomas Gleixner and Kate Stewart and
      Philippe Ombredanne.
      
      How this work was done:
      
      Patches were generated and checked against linux-4.14-rc6 for a subset of
      the use cases:
       - file had no licensing information it it.
       - file was a */uapi/* one with no licensing information in it,
       - file was a */uapi/* one with existing licensing information,
      
      Further patches will be generated in subsequent months to fix up cases
      where non-standard license headers were used, and references to license
      had to be inferred by heuristics based on keywords.
      
      The analysis to determine which SPDX License Identifier to be applied to
      a file was done in a spreadsheet of side by side results from of the
      output of two independent scanners (ScanCode & Windriver) producing SPDX
      tag:value files created by Philippe Ombredanne.  Philippe prepared the
      base worksheet, and did an initial spot review of a few 1000 files.
      
      The 4.13 kernel was the starting point of the analysis with 60,537 files
      assessed.  Kate Stewart did a file by file comparison of the scanner
      results in the spreadsheet to determine which SPDX license identifier(s)
      to be applied to the file. She confirmed any determination that was not
      immediately clear with lawyers working with the Linux Foundation.
      
      Criteria used to select files for SPDX license identifier tagging was:
       - Files considered eligible had to be source code files.
       - Make and config files were included as candidates if they contained >5
         lines of source
       - File already had some variant of a license header in it (even if <5
         lines).
      
      All documentation files were explicitly excluded.
      
      The following heuristics were used to determine which SPDX license
      identifiers to apply.
      
       - when both scanners couldn't find any license traces, file was
         considered to have no license information in it, and the top level
         COPYING file license applied.
      
         For non */uapi/* files that summary was:
      
         SPDX license identifier                            # files
         ---------------------------------------------------|-------
         GPL-2.0                                              11139
      
         and resulted in the first patch in this series.
      
         If that file was a */uapi/* path one, it was "GPL-2.0 WITH
         Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:
      
         SPDX license identifier                            # files
         ---------------------------------------------------|-------
         GPL-2.0 WITH Linux-syscall-note                        930
      
         and resulted in the second patch in this series.
      
       - if a file had some form of licensing information in it, and was one
         of the */uapi/* ones, it was denoted with the Linux-syscall-note if
         any GPL family license was found in the file or had no licensing in
         it (per prior point).  Results summary:
      
         SPDX license identifier                            # files
         ---------------------------------------------------|------
         GPL-2.0 WITH Linux-syscall-note                       270
         GPL-2.0+ WITH Linux-syscall-note                      169
         ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
         ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
         LGPL-2.1+ WITH Linux-syscall-note                      15
         GPL-1.0+ WITH Linux-syscall-note                       14
         ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
         LGPL-2.0+ WITH Linux-syscall-note                       4
         LGPL-2.1 WITH Linux-syscall-note                        3
         ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
         ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1
      
         and that resulted in the third patch in this series.
      
       - when the two scanners agreed on the detected license(s), that became
         the concluded license(s).
      
       - when there was disagreement between the two scanners (one detected a
         license but the other didn't, or they both detected different
         licenses) a manual inspection of the file occurred.
      
       - In most cases a manual inspection of the information in the file
         resulted in a clear resolution of the license that should apply (and
         which scanner probably needed to revisit its heuristics).
      
       - When it was not immediately clear, the license identifier was
         confirmed with lawyers working with the Linux Foundation.
      
       - If there was any question as to the appropriate license identifier,
         the file was flagged for further research and to be revisited later
         in time.
      
      In total, over 70 hours of logged manual review was done on the
      spreadsheet to determine the SPDX license identifiers to apply to the
      source files by Kate, Philippe, Thomas and, in some cases, confirmation
      by lawyers working with the Linux Foundation.
      
      Kate also obtained a third independent scan of the 4.13 code base from
      FOSSology, and compared selected files where the other two scanners
      disagreed against that SPDX file, to see if there was new insights.  The
      Windriver scanner is based on an older version of FOSSology in part, so
      they are related.
      
      Thomas did random spot checks in about 500 files from the spreadsheets
      for the uapi headers and agreed with SPDX license identifier in the
      files he inspected. For the non-uapi files Thomas did random spot checks
      in about 15000 files.
      
      In initial set of patches against 4.14-rc6, 3 files were found to have
      copy/paste license identifier errors, and have been fixed to reflect the
      correct identifier.
      
      Additionally Philippe spent 10 hours this week doing a detailed manual
      inspection and review of the 12,461 patched files from the initial patch
      version early this week with:
       - a full scancode scan run, collecting the matched texts, detected
         license ids and scores
       - reviewing anything where there was a license detected (about 500+
         files) to ensure that the applied SPDX license was correct
       - reviewing anything where there was no detection but the patch license
         was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
         SPDX license was correct
      
      This produced a worksheet with 20 files needing minor correction.  This
      worksheet was then exported into 3 different .csv files for the
      different types of files to be modified.
      
      These .csv files were then reviewed by Greg.  Thomas wrote a script to
      parse the csv files and add the proper SPDX tag to the file, in the
      format that the file expected.  This script was further refined by Greg
      based on the output to detect more types of files automatically and to
      distinguish between header and source .c files (which need different
      comment types.)  Finally Greg ran the script using the .csv files to
      generate the patches.
      Reviewed-by: default avatarKate Stewart <kstewart@linuxfoundation.org>
      Reviewed-by: default avatarPhilippe Ombredanne <pombredanne@nexb.com>
      Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      b2441318
  17. 01 Apr, 2017 1 commit
  18. 16 Mar, 2017 1 commit
  19. 09 Mar, 2017 1 commit
  20. 03 Mar, 2017 1 commit
  21. 02 Mar, 2017 1 commit
    • Ingo Molnar's avatar
      kasan, sched/headers: Uninline kasan_enable/disable_current() · af8601ad
      Ingo Molnar authored
      
      
      <linux/kasan.h> is a low level header that is included early
      in affected kernel headers. But it includes <linux/sched.h>
      which complicates the cleanup of sched.h dependencies.
      
      But kasan.h has almost no need for sched.h: its only use of
      scheduler functionality is in two inline functions which are
      not used very frequently - so uninline kasan_enable_current()
      and kasan_disable_current().
      
      Also add a <linux/sched.h> dependency to a .c file that depended
      on kasan.h including it.
      
      This paves the way to remove the <linux/sched.h> include from kasan.h.
      Acked-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      Cc: Mike Galbraith <efault@gmx.de>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: linux-kernel@vger.kernel.org
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      af8601ad
  22. 25 Feb, 2017 1 commit
    • Greg Thelen's avatar
      kasan: drain quarantine of memcg slab objects · f9fa1d91
      Greg Thelen authored
      Per memcg slab accounting and kasan have a problem with kmem_cache
      destruction.
       - kmem_cache_create() allocates a kmem_cache, which is used for
         allocations from processes running in root (top) memcg.
       - Processes running in non root memcg and allocating with either
         __GFP_ACCOUNT or from a SLAB_ACCOUNT cache use a per memcg
         kmem_cache.
       - Kasan catches use-after-free by having kfree() and kmem_cache_free()
         defer freeing of objects. Objects are placed in a quarantine.
       - kmem_cache_destroy() destroys root and non root kmem_caches. It takes
         care to drain the quarantine of objects from the root memcg's
         kmem_cache, but ignores objects associated with non root memcg. This
         causes leaks because quarantined per memcg objects refer to per memcg
         kmem cache being destroyed.
      
      To see the problem:
      
       1) create a slab cache with kmem_cache_create(,,,SLAB_ACCOUNT,)
       2) from non root memcg, allocate and free a few objects from cache
       3) dispose of the cache with kmem_cache_destroy() kmem_cache_destroy()
          will trigger a "Slab cache still has objects" warning indicating
          that the per memcg kmem_cache structure was leaked.
      
      Fix the leak by draining kasan quarantined objects allocated from non
      root memcg.
      
      Racing memcg deletion is tricky, but handled.  kmem_cache_destroy() =>
      shutdown_memcg_caches() => __shutdown_memcg_cache() => shutdown_cache()
      flushes per memcg quarantined objects, even if that memcg has been
      rmdir'd and gone through memcg_deactivate_kmem_caches().
      
      This leak only affects destroyed SLAB_ACCOUNT kmem caches when kasan is
      enabled.  So I don't think it's worth patching stable kernels.
      
      Link: http://lkml.kernel.org/r/1482257462-36948-1-git-send-email-gthelen@google.com
      
      Signed-off-by: default avatarGreg Thelen <gthelen@google.com>
      Reviewed-by: default avatarVladimir Davydov <vdavydov.dev@gmail.com>
      Acked-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
      Cc: Alexander Potapenko <glider@google.com>
      Cc: Dmitry Vyukov <dvyukov@google.com>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      f9fa1d91