Re: [PATCH] Revert "bpf: Take return from set_memory_rox() into account with bpf_jit_binary_lock_ro()" for linux-6.6.37

WangYuli
2024-07-07T07:35:04Z

On 2024/7/6 17:30, Greg KH wrote:
> This makes it sound like you are reverting this because of a build
> error, which is not the case here, right? Isn't this because of the
> powerpc issue reported here:
> https://lore.kernel.org/r/20240705203413.wbv2nw3747vjeibk@altlinux.org
> ?

No, it only occurs on ARM64 architecture. The reason is that before
being modified, the function

bpf_jit_binary_lock_ro() in arch/arm64/net/bpf_jit_comp.c +1651

was introduced with __must_check, which is defined as
__attribute__((__warn_unused_result__)).

However, at this point, calling bpf_jit_binary_lock_ro(header)
coincidentally results in an unused-result

warning.

> If not, why not just backport the single missing arm64 commit,

Upstream commit 1dad391daef1 ("bpf, arm64: use bpf_prog_pack for memory
management") is part of

a larger change that involves multiple commits. It's not an isolated commit.

We could certainly backport all of them to solve this problem, but it's
not the simplest solution.

> and why
> didn't this show up in testing?

Thanks for the tip.

I'll be sure to keep a closer eye on the stable kernel testing phase in
the future and hopefully catch any

problems more timely.

> confused,
>
> greg k-h
>
Sincerely
--
WangYuli <wangyuli@uniontech.com>