Re: [PATCH v2 1/4] bpf: Add support for reading user pointers

From: Joel Fernandes <joel@joelfernandes.org>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: linux-kernel@vger.kernel.org,
	Michal Gregorczyk <michalgr@live.com>,
	Adrian Ratiu <adrian.ratiu@collabora.com>,
	Mohammad Husain <russoue@gmail.com>,
	Qais Yousef <qais.yousef@arm.com>,
	Srinivas Ramana <sramana@codeaurora.org>,
	duyuchao <yuchao.du@unisoc.com>,
	Manjo Raja Rao <linux@manojrajarao.com>,
	Karim Yaghmour <karim.yaghmour@opersys.com>,
	Tamir Carmeli <carmeli.tamir@gmail.com>,
	Yonghong Song <yhs@fb.com>, Alexei Starovoitov <ast@kernel.org>,
	Brendan Gregg <brendan.d.gregg@gmail.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Peter Ziljstra <peterz@infradead.org>,
	Andrii Nakryiko <andrii.nakryiko@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Kees Cook <keescook@chromium.org>,
	kernel-team@android.com, bpf@vger.kernel.org,
	Ingo Molnar <mingo@redhat.com>, Martin KaFai Lau <kafai@fb.com>,
	netdev@vger.kernel.org, Song Liu <songliubraving@fb.com>
Subject: Re: [PATCH v2 1/4] bpf: Add support for reading user pointers
Date: Mon, 6 May 2019 15:57:11 -0400	[thread overview]
Message-ID: <20190506195711.GA48323@google.com> (raw)
In-Reply-To: <3c6b312c-5763-0d9c-7c2c-436ee41f9be1@iogearbox.net>

On Mon, May 06, 2019 at 09:11:19PM +0200, Daniel Borkmann wrote:
> On 05/06/2019 08:31 PM, Joel Fernandes (Google) wrote:
> > The eBPF based opensnoop tool fails to read the file path string passed
> > to the do_sys_open function. This is because it is a pointer to
> > userspace address and causes an -EFAULT when read with
> > probe_kernel_read. This is not an issue when running the tool on x86 but
> > is an issue on arm64. This patch adds a new bpf function call based
> > which calls the recently proposed probe_user_read function [1].
> > Using this function call from opensnoop fixes the issue on arm64.
> > 
> > [1] https://lore.kernel.org/patchwork/patch/1051588/
> > 
> > Cc: Michal Gregorczyk <michalgr@live.com>
> > Cc: Adrian Ratiu <adrian.ratiu@collabora.com>
> > Cc: Mohammad Husain <russoue@gmail.com>
> > Cc: Qais Yousef <qais.yousef@arm.com>
> > Cc: Srinivas Ramana <sramana@codeaurora.org>
> > Cc: duyuchao <yuchao.du@unisoc.com>
> > Cc: Manjo Raja Rao <linux@manojrajarao.com>
> > Cc: Karim Yaghmour <karim.yaghmour@opersys.com>
> > Cc: Tamir Carmeli <carmeli.tamir@gmail.com>
> > Cc: Yonghong Song <yhs@fb.com>
> > Cc: Alexei Starovoitov <ast@kernel.org>
> > Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
> > Cc: Masami Hiramatsu <mhiramat@kernel.org>
> > Cc: Peter Ziljstra <peterz@infradead.org>
> > Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
> > Cc: Steven Rostedt <rostedt@goodmis.org>
> > Cc: Kees Cook <keescook@chromium.org>
> > Cc: kernel-team@android.com
> > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> > ---
> > Masami, could you carry these patches in the series where are you add
> > probe_user_read function?
> > 
> > Previous submissions is here:
> > https://lore.kernel.org/patchwork/patch/1069552/
> > v1->v2: split tools uapi sync into separate commit, added deprecation
> > warning for old bpf_probe_read function.
> 
> Please properly submit this series to bpf tree once the base
> infrastructure from Masami is upstream.

Could you clarify what do you mean by "properly submit this series to bpf
tree" mean? bpf@vger.kernel.org is CC'd.

> This series here should
> also fix up all current probe read usage under samples/bpf/ and
> tools/testing/selftests/bpf/.

Ok. Agreed, will do that.

thanks,

- Joel