Re: [PATCH v2 3/3] bpf: cgroup: restore sysctl new-value replacement

[Yonghong Song]

On 5/28/26 8:10 PM, Dawei Feng wrote:
> Commit 4e63acdff864 ("bpf: Introduce bpf_sysctl_{get,set}_new_value
> helpers") changed the success return value to 0, but failed to update the
> corresponding check in __cgroup_bpf_run_filter_sysctl(). Since
> bpf_prog_run_array_cg() now returns 0 on success, the legacy ret == 1
> condition is never satisfied. As a result, the modified value is ignored,
> and bpf_sysctl_set_new_value() fails to replace the write buffer.
>
> Fix this by checking for a return value of 0 instead, so cgroup/sysctl
> programs can correctly replace the pending sysctl buffer.
>
> This bug was discovered during a manual code review. Tested via a
> cgroup/sysctl BPF reproducer overriding writes to a target sysctl.
> Pre-fix, bpf_sysctl_set_new_value("foo") was silently ignored: the write
> returned 8192 and the value remained "600". Post-fix, the BPF replacement
> buffer properly propagates: the write returns 3 and the value updates to
> "foo".
>
> Fixes: 4e63acdff864 ("bpf: Introduce bpf_sysctl_{get,set}_new_value helpers")

Maybe to have the following commit as the fix tag:
  f10d05966196 ("bpf: Make BPF_PROG_RUN_ARRAY return -err instead of allow boolean")

Also, for subject, please remove ': cgroup' (including the patch 1 and 2).
The 'Restore sysctl new-value replacement' is not really clear.
Maybe 'bpf: Restore sysctl new-value from 1 to 0'?
Other than the above,

Acked-by: Yonghong Song <yonghong.song@xxxxxxxxx>