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git.odroid.com / linux / 2246168a72ec76f45c4b27016be238ba988ea94a
commit2246168a72ec76f45c4b27016be238ba988ea94a[log] [tgz]
authorDezhi Huang <huangdezhi@hihonor.com>Mon May 22 21:24:45 2023 +0800
committerSuren Baghdasaryan <surenb@google.com>Mon Jun 05 16:43:02 2023 +0000
treee85372ff131ef051b8c88343dfa980f390e8dbeb
parent7cc458acf42c60f417156694c4e5a43a99d5cfe1 [diff]
ANDROID: fix a race between speculative page walk and unmap operations

Speculative page fault walks the page tables under RCU protection and
assumes that page tables are stable after ptl lock is taken. Current
implementation has three issues:
1. While pmd can't be destroyed while in RCU read section, it can be
cleared and result in an invalid ptl lock address. Fix that by
rechecking pmd value after obtaining ptl lock.
2. In case of CONFIG_ALLOC_SPLIT_PTLOCKS, ptl lock is separate from the
pmd and is destroyed by a synchronous call to pgtable_pmd_page_dtor,
which can happen while page walker is in RCU section. Prevent this by
adding a dependency for CONFIG_SPECULATIVE_PAGE_FAULT to require
!CONIG_ALLOC_SPLIT_PTLOCKS.
3. Below sequence when do_mmap happens after the last mmap_seq check
would result in use-after-free issue.

__pte_map_lock
      rcu_read_lock()
      mmap_seq_read_check()

      ptl = pte_lockptr(vmf->pmd)

      spin_trylock(ptl)
      mmap_seq_read_check()
                             mmap_write_lock()
                             do_mmap()
                               unmap_region()
                                 unmap_vmas()
                                 free_pgtables()
                                   ...
                                   free_pte_range
                                   pmd_clear
                                     pte_free_tlb
                                        ...
                                        call_rcu(tlb_remove_table_rcu)

      rcu_read_unlock()
                             tlb_remove_table_rcu
      spin_unlock(ptl) <-- UAF!

To prevent that free_pte_range needs to be blocked if ptl is locked and
is in use.

[tyler wang: This is a backport from
https://android-review.googlesource.com/c/kernel/common/+/2330194.
We have adapted the corresponding modifications from 5.15 to 5.10,
including the changes made to the function __pte_map_lock in 5.15, which have
been adapted to the functions pte_spinlock and __pte_map_lock_speculative in
5.10. Additionally, following surenb's suggestion, we have folded
https://android-review.googlesource.com/c/kernel/common/+/2368961 in this patch.]

Bug: 278602292
Change-Id: I7b353f0995fc59e92bb2069bcdc7d1ac29b521b9
Signed-off-by: Dezhi Huang <huangdezhi@hihonor.com>
1 file changed
tree: e85372ff131ef051b8c88343dfa980f390e8dbeb
  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. samples/
  19. scripts/
  20. security/
  21. sound/
  22. tools/
  23. usr/
  24. virt/
  25. .clang-format
  26. .cocciconfig
  27. .get_maintainer.ignore
  28. .gitattributes
  29. .gitignore
  30. .mailmap
  31. build.config.aarch64
  32. build.config.allmodconfig
  33. build.config.allmodconfig.aarch64
  34. build.config.allmodconfig.arm
  35. build.config.allmodconfig.x86_64
  36. build.config.amlogic
  37. build.config.arm
  38. build.config.common
  39. build.config.db845c
  40. build.config.gki
  41. build.config.gki-debug.aarch64
  42. build.config.gki-debug.x86_64
  43. build.config.gki.aarch64
  44. build.config.gki.aarch64.fips140
  45. build.config.gki.aarch64.fips140_eval_testing
  46. build.config.gki.x86_64
  47. build.config.gki_kasan
  48. build.config.gki_kasan.aarch64
  49. build.config.gki_kasan.x86_64
  50. build.config.gki_kprobes
  51. build.config.gki_kprobes.aarch64
  52. build.config.gki_kprobes.x86_64
  53. build.config.hikey960
  54. build.config.khwasan
  55. build.config.rockchip
  56. build.config.x86_64
  57. COPYING
  58. CREDITS
  59. Kbuild
  60. Kconfig
  61. MAINTAINERS
  62. Makefile
  63. OWNERS
  64. README
  65. 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)