Merge branch 'bpf-refcount-followups-2-owner-field'

Merge branch 'bpf-refcount-followups-2-owner-field'

Dave Marchevsky says:

====================
BPF Refcount followups 2: owner field

This series adds an 'owner' field to bpf_{list,rb}_node structs, to be
used by the runtime to determine whether insertion or removal operations
are valid in shared ownership scenarios. Both the races which the series
fixes and the fix itself are inspired by Kumar's suggestions in [0].

Aside from insertion and removal having more reasons to fail, there are
no user-facing changes as a result of this series.

* Patch 1 reverts disabling of bpf_refcount_acquire so that the fixed
logic can be exercised by CI. It should _not_ be applied.
* Patch 2 adds internal definitions of bpf_{rb,list}_node so that
their fields are easier to access.
* Patch 3 is the meat of the series - it adds 'owner' field and
enforcement of correct owner to insertion and removal helpers.
* Patch 4 adds a test based on Kumar's examples.
* Patch 5 disables the test until bpf_refcount_acquire is re-enabled.
* Patch 6 reverts disabling of test added in this series
logic can be exercised by CI. It should _not_ be applied.

  [0]: https://lore.kernel.org/bpf/d7hyspcow5wtjcmw4fugdgyp3fwhljwuscp3xyut5qnwivyeru@ysdq543otzv2/

Changelog:

v1 -> v2: lore.kernel.org/bpf/20230711175945.3298231-1-davemarchevsky@fb.com/

Patch 2 ("Introduce internal definitions for UAPI-opaque bpf_{rb,list}_node")
  * Rename bpf_{rb,list}_node_internal -> bpf_{list,rb}_node_kern (Alexei)

Patch 3 ("bpf: Add 'owner' field to bpf_{list,rb}_node")
  * WARN_ON_ONCE in __bpf_list_del when node has wrong owner. This shouldn't
    happen, but worth checking regardless (Alexei, offline convo)
  * Continue previous patch's renaming changes
====================

Link: https://lore.kernel.org/r/20230718083813.3416104-1-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>