netdev - Re: [PATCH] Revert "bpf: Take return from set_memory_rox() into account with bpf_jit_binary_lock

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Message-ID: <2024070815-udder-charging-7f75@gregkh>
Date: Mon, 8 Jul 2024 14:36:39 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: WangYuli <wangyuli@...ontech.com>
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Subject: Re: [PATCH] Revert "bpf: Take return from set_memory_rox() into
 account with bpf_jit_binary_lock_ro()" for linux-6.6.37

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