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android / kernel / common / refs/tags/android12-5.10-2022-10_r2
tag8378c78ea705c1b26c1699b7abfb493850cdd589
taggerHoward Chen <howardsoc@google.com>Wed Nov 09 15:16:05 2022 +0800
objectaff80ec64dc03305bbac81b608d8aa1920de2412 
android12-5.10 October 2022 release 2

Artifacts:
  https://ci.android.com/builds/submitted/9258886/kernel_aarch64/latest
commitaff80ec64dc03305bbac81b608d8aa1920de2412[log] [tgz]
authorCarlos Llamas <cmllamas@google.com>Fri Nov 04 17:54:49 2022 +0000
committerCarlos Llamas <cmllamas@google.com>Fri Nov 04 23:38:34 2022 +0000
tree9efa593e06f56a486bbcee638f911096ad6ece58
parent3335f95077ab2dc88450db41f674c827a22639e7 [diff]
FROMLIST: binder: fix UAF of alloc->vma in race with munmap()

In commit 720c24192404 ("ANDROID: binder: change down_write to
down_read") binder assumed the mmap read lock is sufficient to protect
alloc->vma inside binder_update_page_range(). This used to be accurate
until commit dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in
munmap"), which now downgrades the mmap_lock after detaching the vma
from the rbtree in munmap(). Then it proceeds to teardown and free the
vma with only the read lock held.

This means that accesses to alloc->vma in binder_update_page_range() now
will race with vm_area_free() in munmap() and can cause a UAF as shown
in the following KASAN trace:

  ==================================================================
  BUG: KASAN: use-after-free in vm_insert_page+0x7c/0x1f0
  Read of size 8 at addr ffff16204ad00600 by task server/558

  CPU: 3 PID: 558 Comm: server Not tainted 5.10.150-00001-gdc8dcf942daa #1
  Hardware name: linux,dummy-virt (DT)
  Call trace:
   dump_backtrace+0x0/0x2a0
   show_stack+0x18/0x2c
   dump_stack+0xf8/0x164
   print_address_description.constprop.0+0x9c/0x538
   kasan_report+0x120/0x200
   __asan_load8+0xa0/0xc4
   vm_insert_page+0x7c/0x1f0
   binder_update_page_range+0x278/0x50c
   binder_alloc_new_buf+0x3f0/0xba0
   binder_transaction+0x64c/0x3040
   binder_thread_write+0x924/0x2020
   binder_ioctl+0x1610/0x2e5c
   __arm64_sys_ioctl+0xd4/0x120
   el0_svc_common.constprop.0+0xac/0x270
   do_el0_svc+0x38/0xa0
   el0_svc+0x1c/0x2c
   el0_sync_handler+0xe8/0x114
   el0_sync+0x180/0x1c0

  Allocated by task 559:
   kasan_save_stack+0x38/0x6c
   __kasan_kmalloc.constprop.0+0xe4/0xf0
   kasan_slab_alloc+0x18/0x2c
   kmem_cache_alloc+0x1b0/0x2d0
   vm_area_alloc+0x28/0x94
   mmap_region+0x378/0x920
   do_mmap+0x3f0/0x600
   vm_mmap_pgoff+0x150/0x17c
   ksys_mmap_pgoff+0x284/0x2dc
   __arm64_sys_mmap+0x84/0xa4
   el0_svc_common.constprop.0+0xac/0x270
   do_el0_svc+0x38/0xa0
   el0_svc+0x1c/0x2c
   el0_sync_handler+0xe8/0x114
   el0_sync+0x180/0x1c0

  Freed by task 560:
   kasan_save_stack+0x38/0x6c
   kasan_set_track+0x28/0x40
   kasan_set_free_info+0x24/0x4c
   __kasan_slab_free+0x100/0x164
   kasan_slab_free+0x14/0x20
   kmem_cache_free+0xc4/0x34c
   vm_area_free+0x1c/0x2c
   remove_vma+0x7c/0x94
   __do_munmap+0x358/0x710
   __vm_munmap+0xbc/0x130
   __arm64_sys_munmap+0x4c/0x64
   el0_svc_common.constprop.0+0xac/0x270
   do_el0_svc+0x38/0xa0
   el0_svc+0x1c/0x2c
   el0_sync_handler+0xe8/0x114
   el0_sync+0x180/0x1c0

  [...]
  ==================================================================

To prevent the race above, revert back to taking the mmap write lock
inside binder_update_page_range(). One might expect an increase of mmap
lock contention. However, binder already serializes these calls via top
level alloc->mutex. Also, there was no performance impact shown when
running the binder benchmark tests.

Note this patch is specific to stable branches 5.4 and 5.10. Since in
newer kernel releases binder no longer caches a pointer to the vma.
Instead, it has been refactored to use vma_lookup() which avoids the
issue described here. This switch was introduced in commit a43cfc87caaf
("android: binder: stop saving a pointer to the VMA").

Bug: 254837884
Link: https://lore.kernel.org/all/20221104175450.306810-1-cmllamas@google.com/
Fixes: dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap")
Reported-by: Jann Horn <jannh@google.com>
Cc: <stable@vger.kernel.org> # 5.10.x
Cc: Minchan Kim <minchan@kernel.org>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Change-Id: Ieabadbfa30f99812da9c226cf1ddd5e60f62c607
(cherry picked from commit b684150a44187376ae2ea8369c400140ffc3ea67)
1 file changed
tree: 9efa593e06f56a486bbcee638f911096ad6ece58
  1. android/
  2. arch/
  3. block/
  4. certs/
  5. crypto/
  6. Documentation/
  7. drivers/
  8. fs/
  9. include/
  10. init/
  11. ipc/
  12. kernel/
  13. lib/
  14. LICENSES/
  15. mm/
  16. net/
  17. samples/
  18. scripts/
  19. security/
  20. sound/
  21. tools/
  22. usr/
  23. virt/
  24. .clang-format
  25. .cocciconfig
  26. .get_maintainer.ignore
  27. .gitattributes
  28. .gitignore
  29. .mailmap
  30. build.config.aarch64
  31. build.config.allmodconfig
  32. build.config.allmodconfig.aarch64
  33. build.config.allmodconfig.arm
  34. build.config.allmodconfig.x86_64
  35. build.config.amlogic
  36. build.config.arm
  37. build.config.common
  38. build.config.db845c
  39. build.config.gki
  40. build.config.gki-debug.aarch64
  41. build.config.gki-debug.x86_64
  42. build.config.gki.aarch64
  43. build.config.gki.aarch64.fips140
  44. build.config.gki.aarch64.fips140_eval_testing
  45. build.config.gki.x86_64
  46. build.config.gki_kasan
  47. build.config.gki_kasan.aarch64
  48. build.config.gki_kasan.x86_64
  49. build.config.gki_kprobes
  50. build.config.gki_kprobes.aarch64
  51. build.config.gki_kprobes.x86_64
  52. build.config.hikey960
  53. build.config.khwasan
  54. build.config.rockchip
  55. build.config.x86_64
  56. COPYING
  57. CREDITS
  58. Kbuild
  59. Kconfig
  60. MAINTAINERS
  61. Makefile
  62. OWNERS
  63. README
  64. README.md
README.md

How do I submit patches to Android Common Kernels

  1. BEST: Make all of your changes to upstream Linux. If appropriate, backport to the stable releases. These patches will be merged automatically in the corresponding common kernels. If the patch is already in upstream Linux, post a backport of the patch that conforms to the patch requirements below.

    • Do not send patches upstream that contain only symbol exports. To be considered for upstream Linux, additions of EXPORT_SYMBOL_GPL() require an in-tree modular driver that uses the symbol -- so include the new driver or changes to an existing driver in the same patchset as the export.
    • When sending patches upstream, the commit message must contain a clear case for why the patch is needed and beneficial to the community. Enabling out-of-tree drivers or functionality is not not a persuasive case.

  2. LESS GOOD: Develop your patches out-of-tree (from an upstream Linux point-of-view). Unless these are fixing an Android-specific bug, these are very unlikely to be accepted unless they have been coordinated with kernel-team@android.com. If you want to proceed, post a patch that conforms to the patch requirements below.

Common Kernel patch requirements

  • All patches must conform to the Linux kernel coding standards and pass script/checkpatch.pl
  • Patches shall not break gki_defconfig or allmodconfig builds for arm, arm64, x86, x86_64 architectures (see https://source.android.com/setup/build/building-kernels)
  • If the patch is not merged from an upstream branch, the subject must be tagged with the type of patch: UPSTREAM:, BACKPORT:, FROMGIT:, FROMLIST:, or ANDROID:.
  • All patches must have a Change-Id: tag (see https://gerrit-review.googlesource.com/Documentation/user-changeid.html)
  • If an Android bug has been assigned, there must be a Bug: tag.
  • All patches must have a Signed-off-by: tag by the author and the submitter

Additional requirements are listed below based on patch type

Requirements for backports from mainline Linux: UPSTREAM:, BACKPORT:

  • If the patch is a cherry-pick from Linux mainline with no changes at all
    • tag the patch subject with UPSTREAM:.
    • add upstream commit information with a (cherry picked from commit ...) line
    • Example:
      • if the upstream commit message is
        important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>
  • then Joe Smith would upload the patch for the common kernel as
        UPSTREAM: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch requires any changes from the upstream version, tag the patch with BACKPORT: instead of UPSTREAM:.
    • use the same tags as UPSTREAM:
    • add comments about the changes under the (cherry picked from commit ...) line
    • Example:
        BACKPORT: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        [joe: Resolved minor conflict in drivers/foo/bar.c ]
        Signed-off-by: Joe Smith <joe.smith@foo.org>

Requirements for other backports: FROMGIT:, FROMLIST:,

  • If the patch has been merged into an upstream maintainer tree, but has not yet been merged into Linux mainline
    • tag the patch subject with FROMGIT:
    • add info on where the patch came from as (cherry picked from commit <sha1> <repo> <branch>). This must be a stable maintainer branch (not rebased, so don't use linux-next for example).
    • if changes were required, use BACKPORT: FROMGIT:
    • Example:
      • if the commit message in the maintainer tree is
        important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>
  • then Joe Smith would upload the patch for the common kernel as
        FROMGIT: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        (cherry picked from commit 878a2fd9de10b03d11d2f622250285c7e63deace
         https://git.kernel.org/pub/scm/linux/kernel/git/foo/bar.git test-branch)
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch has been submitted to LKML, but not accepted into any maintainer tree
    • tag the patch subject with FROMLIST:
    • add a Link: tag with a link to the submittal on lore.kernel.org
    • add a Bug: tag with the Android bug (required for patches not accepted into a maintainer tree)
    • if changes were required, use BACKPORT: FROMLIST:
    • Example:
        FROMLIST: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Link: https://lore.kernel.org/lkml/20190619171517.GA17557@someone.com/
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>

Requirements for Android-specific patches: ANDROID:

  • If the patch is fixing a bug to Android-specific code
    • tag the patch subject with ANDROID:
    • add a Fixes: tag that cites the patch with the bug
    • Example:
        ANDROID: fix android-specific bug in foobar.c

        This is the detailed description of the important fix

        Fixes: 1234abcd2468 ("foobar: add cool feature")
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch is a new feature
    • tag the patch subject with ANDROID:
    • add a Bug: tag with the Android bug (required for android-specific features)