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From: Jiri Olsa <olsajiri@gmail.com>
To: Greg KH <gregkh@linuxfoundation.org>
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: Sun, 28 May 2023 22:02:49 +0200	[thread overview]
Message-ID: <ZHOzaStC0WmTvwL9@krava> (raw)
In-Reply-To: <2023052646-magnetize-equate-2b24@gregkh>

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

upgrade is an option of course, but it's not a big change and we can
have 5.4 working on arm64 as well

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

jirka

WARNING: multiple messages have this Message-ID (diff)
From: Jiri Olsa <olsajiri@gmail.com>
To: Greg KH <gregkh@linuxfoundation.org>
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: Sun, 28 May 2023 22:02:49 +0200	[thread overview]
Message-ID: <ZHOzaStC0WmTvwL9@krava> (raw)
In-Reply-To: <2023052646-magnetize-equate-2b24@gregkh>

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

upgrade is an option of course, but it's not a big change and we can
have 5.4 working on arm64 as well

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

jirka

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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2023-05-28 20:02 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 [this message]
2023-05-28 20:02     ` Jiri Olsa
2023-05-29  8:37     ` Greg KH
2023-05-29  8:37       ` Greg KH

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