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

Greg KH
2024-07-08T12:36:42Z

On Sun, Jul 07, 2024 at 03:34:15PM +0800, WangYuli wrote:
>
> 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.

Ok, thanks, but why is no one else seeing this in their testing?

> > 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.

reverting the change feels wrong in that you will still have the bug
present that it was trying to solve, right? If so, can you then provide
a working version?

thanks,

greg k-h