Re: [PATCH hotfix 6.12 v2 4/8] mm: resolve faulty mmap_region() error path behaviour

[Mark Brown <broonie@kernel.org>]

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On Wed, Oct 23, 2024 at 09:38:29PM +0100, Lorenzo Stoakes wrote:
> The mmap_region() function is somewhat terrifying, with spaghetti-like
> control flow and numerous means by which issues can arise and incomplete
> state, memory leaks and other unpleasantness can occur.

Today's pending-fixes is showing a fairly large set of failures in the
arm64 MTE selftests on all the platforms that have MTE (currently just
the software ones).  Bisection points at this change which is
0967bf7fbd0e0 in -next which seems plausible but I didn't investigate in
any meaingful detail.  There's nothing particularly instructive in the
test logs, just plain reports that the tests failed:

  # # FAIL: mmap allocation
  # # FAIL: memory allocation
  # not ok 17 Check initial tags with private mapping, sync error mode and mmap memory
  # ok 18 Check initial tags with private mapping, sync error mode and mmap/mprotect memory
  # # FAIL: mmap allocation
  # # FAIL: memory allocation
  # not ok 19 Check initial tags with shared mapping, sync error mode and mmap memory
  # ok 20 Check initial tags with shared mapping, sync error mode and mmap/mprotect memory
  # # Totals: pass:18 fail:2 xfail:0 xpass:0 skip:0 error:0
  not ok 42 selftests: arm64: check_buffer_fill # exit=1

(and more, mainly on mmap related things).  A full log for a sample run
on the FVP can be seen at:

  https://lava.sirena.org.uk/scheduler/job/901638#L3693

and one from qemu here:

  https://lava.sirena.org.uk/scheduler/job/901630#L3031

Both of these logs include links to filesystem/firmware images and
command lines to run the model.

Bisects converge cleanly (there's some random extra good commits logged
at the start as my tooling feeds test results it already has on hand
between the good and bad commits into the bisect):

# bad: [6560005f01c3c14aab4c2ce35d97b75796d33d81] Merge branch 'for-linux-next-fixes' of https://gitlab.freedesktop.org/drm/misc/kernel.git
# good: [ea1fda89f5b23734e10c62762990120d5ae23c43] Merge tag 'x86_urgent_for_v6.12_rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
# good: [6668610b4d8ce9a3ee3ed61a9471f62fb5f05bf9] ASoC: Intel: sst: Support LPE0F28 ACPI HID
# good: [2feb023110843acce790e9089e72e9a9503d9fa5] regulator: rtq2208: Fix uninitialized use of regulator_config
# good: [0107f28f135231da22a9ad5756bb16bd5cada4d5] ASoC: Intel: bytcr_rt5640: Add DMI quirk for Vexia Edu Atla 10 tablet
# good: [25f00a13dccf8e45441265768de46c8bf58e08f6] spi: spi-fsl-dspi: Fix crash when not using GPIO chip select
# good: [032532f91a1d06d0750f16c49a9698ef5374a68f] ASoC: codecs: rt5640: Always disable IRQs from rt5640_cancel_work()
# good: [d48696b915527b5bcdd207a299aec03fb037eb17] ASoC: Intel: bytcr_rt5640: Add support for non ACPI instantiated codec
# good: [d0ccf760a405d243a49485be0a43bd5b66ed17e2] spi: geni-qcom: Fix boot warning related to pm_runtime and devres
# good: [f2b5b8201b1545ef92e050735e9c768010d497aa] spi: mtk-snfi: fix kerneldoc for mtk_snand_is_page_ops()
# good: [b5a468199b995bd8ee3c26f169a416a181210c9e] spi: stm32: fix missing device mode capability in stm32mp25
git bisect start '6560005f01c3c14aab4c2ce35d97b75796d33d81' 'ea1fda89f5b23734e10c62762990120d5ae23c43' '6668610b4d8ce9a3ee3ed61a9471f62fb5f05bf9' '2feb023110843acce790e9089e72e9a9503d9fa5' '0107f28f135231da22a9ad5756bb16bd5cada4d5' '25f00a13dccf8e45441265768de46c8bf58e08f6' '032532f91a1d06d0750f16c49a9698ef5374a68f' 'd48696b915527b5bcdd207a299aec03fb037eb17' 'd0ccf760a405d243a49485be0a43bd5b66ed17e2' 'f2b5b8201b1545ef92e050735e9c768010d497aa' 'b5a468199b995bd8ee3c26f169a416a181210c9e'
# bad: [6560005f01c3c14aab4c2ce35d97b75796d33d81] Merge branch 'for-linux-next-fixes' of https://gitlab.freedesktop.org/drm/misc/kernel.git
git bisect bad 6560005f01c3c14aab4c2ce35d97b75796d33d81
# bad: [4a2901b5d394f58cdc60bc25e32c381bb2b83891] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/wireless/wireless.git
git bisect bad 4a2901b5d394f58cdc60bc25e32c381bb2b83891
# bad: [4093d34d740447b23a1ea916dabcf902aa767812] Merge branch 'fs-current' of linux-next
git bisect bad 4093d34d740447b23a1ea916dabcf902aa767812
# bad: [0967bf7fbd0e03cee0525035762150a91ba1bb7c] mm: resolve faulty mmap_region() error path behaviour
git bisect bad 0967bf7fbd0e03cee0525035762150a91ba1bb7c
# good: [633e7df6cfdf97f8acf2a59fbfead01e31d0e492] tools: testing: add expand-only mode VMA test
git bisect good 633e7df6cfdf97f8acf2a59fbfead01e31d0e492
# good: [315add1ace71306a7d8518fd417466d938041ff1] mseal: update mseal.rst
git bisect good 315add1ace71306a7d8518fd417466d938041ff1
# good: [bcbb8b25ab80347994e33c358481e65f95f665fd] mm: fix PSWPIN counter for large folios swap-in
git bisect good bcbb8b25ab80347994e33c358481e65f95f665fd
# good: [8438cf67b86bf8c966f32612a7e12b2eb910396b] mm: unconditionally close VMAs on error
git bisect good 8438cf67b86bf8c966f32612a7e12b2eb910396b
# good: [a220e219d89c2d574ad9ffda627575e11334fede] mm: refactor map_deny_write_exec()
git bisect good a220e219d89c2d574ad9ffda627575e11334fede
# first bad commit: [0967bf7fbd0e03cee0525035762150a91ba1bb7c] mm: resolve faulty mmap_region() error path behaviour

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