From: Greg KH <gregkh@linuxfoundation.org>
To: Jiri Olsa <olsajiri@gmail.com>
Cc: stable@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org,
x86@kernel.org, linux-kernel@vger.kernel.org,
"Masami Hiramatsu" <mhiramat@kernel.org>,
"Tsahee Zidenberg" <tsahee@annapurnalabs.com>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Christoph Hellwig" <hch@lst.de>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Mahé Tardy" <mahe.tardy@isovalent.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH stable 5.4 0/8] bpf: Fix bpf_probe_read/bpf_probe_read_str helpers
Date: Mon, 29 May 2023 09:37:26 +0100 [thread overview]
Message-ID: <2023052947-jubilance-driven-31d8@gregkh> (raw)
In-Reply-To: <ZHOzaStC0WmTvwL9@krava>
On Sun, May 28, 2023 at 10:02:49PM +0200, Jiri Olsa wrote:
> On Fri, May 26, 2023 at 07:54:17PM +0100, Greg KH wrote:
> > 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?
>
> we have a customer running ok on x86 v5.4, but arm64 is broken with
> the same bpf/user space code
Again why can they not use a newer kernel version? What forces this
customer to be stuck with a specific kernel version that spans different
processor types?
> upgrade is an option of course, but it's not a big change and we can
> have 5.4 working on arm64 as well
For loads of other reasons, I'd recommend 5.15 or newer for arm64, so
why not use that?
> I can send out the change that will be closer to upstream changes,
> if that's a concern.. with adding the new probe helpers, which I
> guess is not a problem, because it does not change current API
You are trying to add features to a stable kernel that are not
regression fixes, which is something that we generally do not accept
into stable kernels.
thnaks,
greg k-h
WARNING: multiple messages have this Message-ID (diff)
From: Greg KH <gregkh@linuxfoundation.org>
To: Jiri Olsa <olsajiri@gmail.com>
Cc: stable@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org,
x86@kernel.org, linux-kernel@vger.kernel.org,
"Masami Hiramatsu" <mhiramat@kernel.org>,
"Tsahee Zidenberg" <tsahee@annapurnalabs.com>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Christoph Hellwig" <hch@lst.de>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Mahé Tardy" <mahe.tardy@isovalent.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH stable 5.4 0/8] bpf: Fix bpf_probe_read/bpf_probe_read_str helpers
Date: Mon, 29 May 2023 09:37:26 +0100 [thread overview]
Message-ID: <2023052947-jubilance-driven-31d8@gregkh> (raw)
In-Reply-To: <ZHOzaStC0WmTvwL9@krava>
On Sun, May 28, 2023 at 10:02:49PM +0200, Jiri Olsa wrote:
> On Fri, May 26, 2023 at 07:54:17PM +0100, Greg KH wrote:
> > 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?
>
> we have a customer running ok on x86 v5.4, but arm64 is broken with
> the same bpf/user space code
Again why can they not use a newer kernel version? What forces this
customer to be stuck with a specific kernel version that spans different
processor types?
> upgrade is an option of course, but it's not a big change and we can
> have 5.4 working on arm64 as well
For loads of other reasons, I'd recommend 5.15 or newer for arm64, so
why not use that?
> I can send out the change that will be closer to upstream changes,
> if that's a concern.. with adding the new probe helpers, which I
> guess is not a problem, because it does not change current API
You are trying to add features to a stable kernel that are not
regression fixes, which is something that we generally do not accept
into stable kernels.
thnaks,
greg k-h
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2023-05-29 8:37 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-22 20:33 [RFC PATCH stable 5.4 0/8] bpf: Fix bpf_probe_read/bpf_probe_read_str helpers Jiri Olsa
2023-05-22 20:33 ` Jiri Olsa
2023-05-22 20:33 ` [RFC PATCH stable 5.4 1/8] uaccess: Add strict non-pagefault kernel-space read function Jiri Olsa
2023-05-22 20:33 ` Jiri Olsa
2023-05-22 20:33 ` [RFC PATCH stable 5.4 2/8] bpf: Add probe_read_{user, kernel} and probe_read_{user, kernel}_str helpers Jiri Olsa
2023-05-22 20:33 ` Jiri Olsa
2023-05-22 20:33 ` [RFC PATCH stable 5.4 3/8] bpf: Restrict bpf_probe_read{, str}() only to archs where they work Jiri Olsa
2023-05-22 20:33 ` Jiri Olsa
2023-05-22 20:33 ` [RFC PATCH stable 5.4 4/8] maccess: clarify kerneldoc comments Jiri Olsa
2023-05-22 20:33 ` Jiri Olsa
2023-05-22 20:33 ` [RFC PATCH stable 5.4 5/8] maccess: rename strncpy_from_unsafe_user to strncpy_from_user_nofault Jiri Olsa
2023-05-22 20:33 ` Jiri Olsa
2023-05-22 20:33 ` [RFC PATCH stable 5.4 6/8] maccess: rename strncpy_from_unsafe_strict to strncpy_from_kernel_nofault Jiri Olsa
2023-05-22 20:33 ` Jiri Olsa
2023-05-22 20:33 ` [RFC PATCH stable 5.4 7/8] bpf: rework the compat kernel probe handling Jiri Olsa
2023-05-22 20:33 ` Jiri Olsa
2023-05-22 20:33 ` [RFC PATCH stable 5.4 8/8] bpf: bpf_probe_read_kernel_str() has to return amount of data read on success Jiri Olsa
2023-05-22 20:33 ` Jiri Olsa
2023-05-26 18:54 ` [RFC PATCH stable 5.4 0/8] bpf: Fix bpf_probe_read/bpf_probe_read_str helpers Greg KH
2023-05-26 18:54 ` Greg KH
2023-05-28 20:02 ` Jiri Olsa
2023-05-28 20:02 ` Jiri Olsa
2023-05-29 8:37 ` Greg KH [this message]
2023-05-29 8:37 ` Greg KH
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