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As reported by Kumar in [0], the shared ownership implementation for BPF
programs has some race conditions which need to be addressed before it
can safely be used. This patch does so in a minimal way instead of
ripping out shared ownership entirely, as proper fixes for the issues
raised will follow ASAP, at which point this patch's commit can be
reverted to re-enable shared ownership.
The patch removes the ability to call bpf_refcount_acquire_impl from BPF
programs. Programs can only bump refcount and obtain a new owning
reference using this kfunc, so removing the ability to call it
effectively disables shared ownership.
Instead of changing success / failure expectations for
bpf_refcount-related selftests, this patch just disables them from
running for now.
[0]: https://lore.kernel.org/bpf/d7hyspcow5wtjcmw4fugdgyp3fwhljwuscp3xyut5qnwivyeru@ysdq543otzv2/
Reported-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20230424204321.2680232-1-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Test refcounted local kptr functionality added in previous patches in
the series.
Usecases which pass verification:
* Add refcounted local kptr to both tree and list. Then, read and -
possibly, depending on test variant - delete from tree, then list.
* Also test doing read-and-maybe-delete in opposite order
* Stash a refcounted local kptr in a map_value, then add it to a
rbtree. Read from both, possibly deleting after tree read.
* Add refcounted local kptr to both tree and list. Then, try reading and
deleting twice from one of the collections.
* bpf_refcount_acquire of just-added non-owning ref should work, as
should bpf_refcount_acquire of owning ref just out of bpf_obj_new
Usecases which fail verification:
* The simple successful bpf_refcount_acquire cases from above should
both fail to verify if the newly-acquired owning ref is not dropped
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20230415201811.343116-10-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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