linux-kernel - Re: [PATCH] rwonce: fix crash by removing READ

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Message-ID: <CAHk-=wgJRECUF-7yt9pNxW_bc=4nJcxn5H3duW_HefY3pKwZag@mail.gmail.com>
Date: Wed, 26 Mar 2025 17:49:23 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>, Jann Horn <jannh@...gle.com>, Marco Elver <elver@...gle.com>, 
	Linux-Arch <linux-arch@...r.kernel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rwonce: fix crash by removing READ_ONCE() for unaligned read

On Wed, 26 Mar 2025 at 15:54, Nathan Chancellor <nathan@...nel.org> wrote:
>
> > Put another way: I wonder what other cases may lurk around this all...
>
> That change has caused only one issue that I know of, which was fixed by
> commit d3f450533bbc ("efi: tpm: Avoid READ_ONCE() for accessing the
> event log"). I have not seen any since then until this point and I do
> daily boots of -next with LTO enabled on both of my arm64 test machines.

Ahh, ok. That makes me happier.

I guess unaligned READ_ONCE() code really shouldn't exist in generic
code anyway, since some architectures will fail any unaligned access.

But those architectures tend to not get a lot of testing (they are a
dying breed - good riddance), so "shouldn't exist" doesn't necessarily
equate to really not existing.

          Linus