Potential reverts of 4.19.y stable changes in 18.04

[Stefan Bader]

== SRU Justification ==

Impact: While reviewing patches done as part of stable work there were two changes which came from linux-4.19.y and seemed not quite right for the 4.15 kernel version we have in 18.04/Bionic:

2e1eb7b6e1e0 locking/mutex: clear MUTEX_FLAGS if wait_list is empty due to signal

This change is only in 4.19y and not in 4.14.y despite it is implied that the breaking commit was already in 3.13. It also seems to pair up with a mode of mutex which only got added to 4.19. Although there were no reports yet, which could prove this wrong, it feels like we rather should not take this change without a case where the current code is reported to be wrong.

6c0065eb69de drm/amd/amdgpu: fix refcount leak

The driver in 4.15 does take refcounts the same way as 4.19 does. We are missing 37ac3dc00da0 ("drm/amdgpu: Use device specific BO size & stride check.") which changed that. So we really should revert this one.

Testing: These are proactive reverts, so there is no real test that could be done. However this just moves back to a state which we had before. And for that state we had no bug reports.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-bionic' to 'verification-done-bionic'. If the problem still exists, change the tag 'verification-needed-bionic' to 'verification-failed-bionic'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Stefan Bader (smb)]

As mentioned in the description these are reverts to the state before based on code review. Verified that those are included in the kernel.

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 4.15.0-154.161

---------------
linux (4.15.0-154.161) bionic; urgency=medium

  * bionic/linux: 4.15.0-154.161 -proposed tracker (LP: #1938411)

  * Potential reverts of 4.19.y stable changes in 18.04 (LP: #1938537)
    - SAUCE: Revert "locking/mutex: clear MUTEX_FLAGS if wait_list is empty due to
      signal"
    - SAUCE: Revert "drm/amd/amdgpu: fix refcount leak"

  * Packaging resync (LP: #1786013)
    - [Packaging] resync getabis
    - [Packaging] update helper scripts
    - update dkms package versions

  * btrfs: Automatic balance returns -EUCLEAN and leads to forced readonly
    filesystem (LP: #1934709) // CVE-2019-19036
    - btrfs: Validate child tree block's level and first key
    - btrfs: Detect unbalanced tree with empty leaf before crashing btree
      operations

  * btrfs: Automatic balance returns -EUCLEAN and leads to forced readonly
    filesystem (LP: #1934709)
    - Revert "btrfs: Detect unbalanced tree with empty leaf before crashing btree
      operations"
    - Revert "btrfs: Validate child tree block's level and first key"
    - btrfs: Only check first key for committed tree blocks
    - btrfs: Fix wrong first_key parameter in replace_path

  * Enable fib-onlink-tests.sh and msg_zerocopy.sh in kselftests/net on Bionic
    (LP: #1934759)
    - selftests: Add fib-onlink-tests.sh to TEST_PROGS
    - selftests: net: use TEST_PROGS_EXTENDED
    - selftests/net: enable msg_zerocopy test
    - SAUCE: selftests: Make fib-onlink-tests.sh executable

  * Kernel oops due to uninitialized list on kernfs (kernfs_kill_sb)
    (LP: #1934175)
    - kernfs: deal with kernfs_fill_super() failures
    - unfuck sysfs_mount()

  * large_dir in ext4 broken (LP: #1933074)
    - SAUCE: ext4: fix directory index node split corruption

  * btrfs: Attempting to balance a nearly full filesystem with relocated root
    nodes fails (LP: #1933172) // CVE-2019-19036
    - btrfs: reloc: fix reloc root leak and NULL pointer dereference

  * btrfs: Attempting to balance a nearly full filesystem with relocated root
    nodes fails (LP: #1933172)
    - Revert "btrfs: reloc: fix reloc root leak and NULL pointer dereference"

  * Pixel format change broken for Elgato Cam Link 4K (LP: #1932367)
    - (upstream) media: uvcvideo: Fix pixel format change for Elgato Cam Link 4K

  * Bionic update: upstream stable patchset 2021-06-23 (LP: #1933375)
    - net: usb: cdc_ncm: don't spew notifications
    - efi: Allow EFI_MEMORY_XP and EFI_MEMORY_RO both to be cleared
    - efi: cper: fix snprintf() use in cper_dimm_err_location()
    - vfio/pci: Fix error return code in vfio_ecap_init()
    - vfio/pci: zap_vma_ptes() needs MMU
    - vfio/platform: fix module_put call in error flow
    - ipvs: ignore IP_VS_SVC_F_HASHED flag when adding service
    - HID: pidff: fix error return code in hid_pidff_init()
    - HID: i2c-hid: fix format string mismatch
    - netfilter: nfnetlink_cthelper: hit EBUSY on updates if size mismatches
    - ieee802154: fix error return code in ieee802154_add_iface()
    - ieee802154: fix error return code in ieee802154_llsec_getparams()
    - Bluetooth: fix the erroneous flush_work() order
    - Blu...