Re: [PATCH v3 bpf-next 1/5] bpf: Let callers of btf_parse_kptr() track life cycle of prog btf

[Martin KaFai Lau <martin.lau@linux.dev>]

On 8/9/24 4:06 PM, Martin KaFai Lau wrote:
> On 8/8/24 5:51 PM, Amery Hung wrote:
>> btf_parse_kptr() and btf_record_free() do btf_get() and btf_put()
>> respectively when working on btf_record in program and map if there are
>> kptr fields. If the kptr is from program BTF, since both callers has
>> already tracked the life cycle of program BTF, it is safe to remove the
>> btf_get() and btf_put().
>>
>> This change prevents memory leak of program BTF later when we start
>> searching for kptr fields when building btf_record for program. It can
>> happen when the btf fd is closed. The btf_put() corresponding to the
>> btf_get() in btf_parse_kptr() was supposed to be called by
>> btf_record_free() in btf_free_struct_meta_tab() in btf_free(). However,
>> it will never happen since the invocation of btf_free() depends on the
>> refcount of the btf to become 0 in the first place.
>>
>> Signed-off-by: Amery Hung <amery.hung@bytedance.com>
> 
> Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
> 
> Need to fix the checkpatch warning though:
> 
> WARNING: From:/Signed-off-by: email address mismatch: 'From: Amery Hung 
> <ameryhung@gmail.com>' != 'Signed-off-by: Amery Hung <amery.hung@bytedance.com>'
> 

There is a veristat failure also:

https://github.com/kernel-patches/bpf/actions/runs/10311824065/job/28546213338

|File                  |Program                         |Verdict                |States Diff (%)|
|----------------------|--------------------------------|-----------------------|---------------|
|local_kptr_stash.bpf.o|refcount_acquire_without_unstash|success -> failure (!!)|-100.00 %      |
|local_kptr_stash.bpf.o|stash_local_with_root           |success -> failure (!!)|-100.00 %      |
|local_kptr_stash.bpf.o|stash_plain                     |success -> failure (!!)|-100.00 %      |
|local_kptr_stash.bpf.o|stash_rb_nodes                  |success -> failure (!!)|-100.00 %      |
|local_kptr_stash.bpf.o|stash_refcounted_node           |success -> failure (!!)|-100.00 %      |
|local_kptr_stash.bpf.o|stash_test_ref_kfunc            |success -> failure (!!)|-100.00 %      |
|local_kptr_stash.bpf.o|unstash_rb_node                 |success -> failure (!!)|-100.00 %      |