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android / kernel / common / 1ca1130ec62d
commit1ca1130ec62da7638497478539c0f55ffbbf9a5e[log] [tgz]
authorCarlos Llamas <cmllamas@google.com>Fri May 05 06:48:10 2023 +0000
committerTreehugger Robot <treehugger-gerrit@google.com>Fri May 05 23:19:06 2023 +0000
tree7b67b03be07e15952f02d3e0c0b822b76f75c033
parent2431799f21a1a1edb180876ff4d8a6d9d66deef5 [diff]
FROMLIST: binder: fix UAF caused by faulty buffer cleanup

In binder_transaction_buffer_release() the 'failed_at' offset indicates
the number of objects to clean up. However, this function was changed by
commit 44d8047f1d87 ("binder: use standard functions to allocate fds"),
to release all the objects in the buffer when 'failed_at' is zero.

This introduced an issue when a transaction buffer is released without
any objects having been processed so far. In this case, 'failed_at' is
indeed zero yet it is misinterpreted as releasing the entire buffer.

This leads to use-after-free errors where nodes are incorrectly freed
and subsequently accessed. Such is the case in the following KASAN
report:

  ==================================================================
  BUG: KASAN: slab-use-after-free in binder_thread_read+0xc40/0x1f30
  Read of size 8 at addr ffff4faf037cfc58 by task poc/474

  CPU: 6 PID: 474 Comm: poc Not tainted 6.3.0-12570-g7df047b3f0aa #5
  Hardware name: linux,dummy-virt (DT)
  Call trace:
   dump_backtrace+0x94/0xec
   show_stack+0x18/0x24
   dump_stack_lvl+0x48/0x60
   print_report+0xf8/0x5b8
   kasan_report+0xb8/0xfc
   __asan_load8+0x9c/0xb8
   binder_thread_read+0xc40/0x1f30
   binder_ioctl+0xd9c/0x1768
   __arm64_sys_ioctl+0xd4/0x118
   invoke_syscall+0x60/0x188
  [...]

  Allocated by task 474:
   kasan_save_stack+0x3c/0x64
   kasan_set_track+0x2c/0x40
   kasan_save_alloc_info+0x24/0x34
   __kasan_kmalloc+0xb8/0xbc
   kmalloc_trace+0x48/0x5c
   binder_new_node+0x3c/0x3a4
   binder_transaction+0x2b58/0x36f0
   binder_thread_write+0x8e0/0x1b78
   binder_ioctl+0x14a0/0x1768
   __arm64_sys_ioctl+0xd4/0x118
   invoke_syscall+0x60/0x188
  [...]

  Freed by task 475:
   kasan_save_stack+0x3c/0x64
   kasan_set_track+0x2c/0x40
   kasan_save_free_info+0x38/0x5c
   __kasan_slab_free+0xe8/0x154
   __kmem_cache_free+0x128/0x2bc
   kfree+0x58/0x70
   binder_dec_node_tmpref+0x178/0x1fc
   binder_transaction_buffer_release+0x430/0x628
   binder_transaction+0x1954/0x36f0
   binder_thread_write+0x8e0/0x1b78
   binder_ioctl+0x14a0/0x1768
   __arm64_sys_ioctl+0xd4/0x118
   invoke_syscall+0x60/0x188
  [...]
  ==================================================================

In order to avoid these issues, let's always calculate the intended
'failed_at' offset beforehand. This is renamed and wrapped in a helper
function to make it clear and convenient.

Fixes: 32e9f56a96d8 ("binder: don't detect sender/target during buffer cleanup")
Reported-by: Zi Fan Tan <zifantan@google.com>
Link: https://b.corp.google.com/issues/275041864
Cc: stable@vger.kernel.org
Signed-off-by: Carlos Llamas <cmllamas@google.com>

Bug: 275041864
Link: https://lore.kernel.org/all/20230505203020.4101154-1-cmllamas@google.com
Change-Id: I4bcc8bde77a8118872237d100cccb5caf95d99a1
Signed-off-by: Carlos Llamas <cmllamas@google.com>
1 file changed
tree: 7b67b03be07e15952f02d3e0c0b822b76f75c033
  1. android/
  2. arch/
  3. block/
  4. certs/
  5. crypto/
  6. Documentation/
  7. drivers/
  8. fs/
  9. include/
  10. init/
  11. io_uring/
  12. ipc/
  13. kernel/
  14. lib/
  15. LICENSES/
  16. mm/
  17. net/
  18. rust/
  19. samples/
  20. scripts/
  21. security/
  22. sound/
  23. tools/
  24. usr/
  25. virt/
  26. .clang-format
  27. .cocciconfig
  28. .get_maintainer.ignore
  29. .gitattributes
  30. .gitignore
  31. .mailmap
  32. .rustfmt.toml
  33. BUILD.bazel
  34. build.config.aarch64
  35. build.config.allmodconfig
  36. build.config.allmodconfig.aarch64
  37. build.config.allmodconfig.arm
  38. build.config.allmodconfig.x86_64
  39. build.config.amlogic
  40. build.config.arm
  41. build.config.common
  42. build.config.constants
  43. build.config.db845c
  44. build.config.gki
  45. build.config.gki-debug.aarch64
  46. build.config.gki-debug.x86_64
  47. build.config.gki.aarch64
  48. build.config.gki.aarch64.16k
  49. build.config.gki.aarch64.fips140
  50. build.config.gki.riscv64
  51. build.config.gki.x86_64
  52. build.config.gki_kasan
  53. build.config.gki_kasan.aarch64
  54. build.config.gki_kasan.x86_64
  55. build.config.gki_kprobes
  56. build.config.gki_kprobes.aarch64
  57. build.config.gki_kprobes.x86_64
  58. build.config.khwasan
  59. build.config.riscv64
  60. build.config.rockpi4
  61. build.config.x86_64
  62. COPYING
  63. CREDITS
  64. Kbuild
  65. Kconfig
  66. Kconfig.ext
  67. MAINTAINERS
  68. Makefile
  69. modules.bzl
  70. OWNERS
  71. OWNERS_DrNo
  72. README
  73. 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 scripts/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)