linux-kernel - Re: [RFC PATCH stable 5.4 0/8] bpf: Fix bpf_probe_read/bpf_probe_read

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Message-ID: <2023052646-magnetize-equate-2b24@gregkh>
Date:   Fri, 26 May 2023 19:54:17 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     stable@...r.kernel.org, linux-mm@...ck.org, bpf@...r.kernel.org,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Tsahee Zidenberg <tsahee@...apurnalabs.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Christoph Hellwig <hch@....de>,
        Daniel Borkmann <daniel@...earbox.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mahé Tardy <mahe.tardy@...valent.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH stable 5.4 0/8] bpf: Fix
 bpf_probe_read/bpf_probe_read_str helpers

On Mon, May 22, 2023 at 10:33:44PM +0200, Jiri Olsa wrote:
> hi,
> we see broken access to user space with bpf_probe_read/bpf_probe_read_str
> helpers on arm64 with 5.4 kernel. The problem is that both helpers try to
> read user memory by calling probe_kernel_read, which seems to work on x86
> but fails on arm64.

Has this ever worked on arm64 for the 5.4 kernel tree?  If not, it's not
really a regression, and so, why not use a newer kernel that has this
new feature added to it there?

In other words, what requires you to use the 5.4.y tree and requires
feature parity across architectures?

thanks,

greg k-h