From: Linus Torvalds <torvalds@linux-foundation.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Andy Lutomirski <luto@amacapital.net>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
stable <stable@vger.kernel.org>,
Changbin Du <changbin.du@gmail.com>, Jann Horn <jannh@google.com>,
Kees Cook <keescook@chromium.org>,
Andy Lutomirski <luto@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Netdev <netdev@vger.kernel.org>,
bpf@vger.kernel.org
Subject: Re: [PATCH 1/2 v2] kprobe: Do not use uaccess functions to access kernel memory that can fault
Date: Fri, 22 Feb 2019 13:20:58 -0800 [thread overview]
Message-ID: <CAHk-=wib9VSbwbS+N82ZPNtvt4vrvYyHyQduhFimX8nyjCyZyA@mail.gmail.com> (raw)
In-Reply-To: <20190222192703.epvgxghwybte7gxs@ast-mbp.dhcp.thefacebook.com>
On Fri, Feb 22, 2019 at 11:27 AM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On bpf side the bpf_probe_read() helper just calls probe_kernel_read()
> and users pass both user and kernel addresses into it and expect
> that the helper will actually try to read from that address.
As mentioned earlier in the thread, that's actually fundamentally broken.
There are architectures that have physically separate address spaces,
with the same pointer value in both kernel and user space.
They are rare, but they exist. At least sparc32 and the old 4G:4G split x86.
So a pointer really should always unambiguously always be explicitly
_either_ a kernel pointer, or a user pointer. You can't have "this is
a pointer", and then try to figure it out by looking at the value.
That may happen to work on x86-64, but it's literally a "happen to
work on the most common architectures", not a design thing.
Linus
next prev parent reply other threads:[~2019-02-22 21:21 UTC|newest]
Thread overview: 85+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-15 17:47 [PATCH 0/2 v2] [GIT PULL (take two)] tracing: Two more fixes Steven Rostedt
2019-02-15 17:47 ` [PATCH 1/2 v2] kprobe: Do not use uaccess functions to access kernel memory that can fault Steven Rostedt
2019-02-15 17:55 ` Linus Torvalds
2019-02-15 22:15 ` Steven Rostedt
2019-02-15 23:49 ` Andy Lutomirski
2019-02-16 0:19 ` Steven Rostedt
2019-02-16 1:32 ` Andy Lutomirski
2019-02-16 2:08 ` Steven Rostedt
2019-02-16 2:14 ` Andy Lutomirski
2019-02-16 2:21 ` Steven Rostedt
2019-02-18 17:58 ` Linus Torvalds
2019-02-18 18:23 ` Linus Torvalds
2019-02-19 16:18 ` Steven Rostedt
2019-02-19 18:43 ` Linus Torvalds
2019-02-19 19:03 ` Steven Rostedt
2019-02-20 8:10 ` Masami Hiramatsu
2019-02-20 13:57 ` Jann Horn
2019-02-20 14:47 ` Steven Rostedt
2019-02-20 15:08 ` Masami Hiramatsu
2019-02-20 14:49 ` Steven Rostedt
2019-02-20 16:04 ` Masami Hiramatsu
2019-02-20 16:42 ` Steven Rostedt
2019-02-21 7:37 ` Masami Hiramatsu
2019-02-22 8:27 ` Masami Hiramatsu
2019-02-22 8:35 ` Masami Hiramatsu
2019-02-22 17:43 ` Linus Torvalds
2019-02-22 17:48 ` Andy Lutomirski
2019-02-22 18:28 ` Linus Torvalds
2019-02-22 19:52 ` Andy Lutomirski
2019-02-22 19:27 ` Alexei Starovoitov
2019-02-22 19:30 ` Steven Rostedt
2019-02-22 19:34 ` Alexei Starovoitov
2019-02-22 19:39 ` Steven Rostedt
2019-02-22 19:55 ` Andy Lutomirski
2019-02-22 21:43 ` Jann Horn
2019-02-22 22:08 ` Nadav Amit
2019-02-22 22:17 ` Jann Horn
2019-02-22 22:21 ` Nadav Amit
2019-02-22 22:39 ` Nadav Amit
2019-02-22 23:02 ` Jann Horn
2019-02-22 23:22 ` Nadav Amit
2019-02-22 23:59 ` Andy Lutomirski
2019-02-23 0:03 ` Alexei Starovoitov
2019-02-23 0:15 ` Nadav Amit
2019-02-24 19:35 ` Andy Lutomirski
2019-02-25 13:36 ` Masami Hiramatsu
2019-02-22 21:20 ` Linus Torvalds [this message]
2019-02-22 21:38 ` David Miller
2019-02-22 21:59 ` Linus Torvalds
2019-02-22 22:51 ` Alexei Starovoitov
2019-02-22 23:11 ` Jann Horn
2019-02-22 23:16 ` David Miller
2019-02-22 23:16 ` Linus Torvalds
2019-02-22 23:56 ` Alexei Starovoitov
2019-02-23 0:08 ` Linus Torvalds
2019-02-23 2:28 ` Alexei Starovoitov
2019-02-23 2:32 ` Linus Torvalds
2019-02-23 3:02 ` Steven Rostedt
2019-02-23 4:51 ` Masami Hiramatsu
2019-02-26 3:57 ` Christoph Hellwig
2019-02-26 15:24 ` Joel Fernandes
2019-02-28 12:29 ` Masami Hiramatsu
2019-02-28 15:18 ` Joel Fernandes
2019-02-23 3:47 ` Masami Hiramatsu
2019-02-24 0:44 ` Steven Rostedt
2019-02-24 4:38 ` Andy Lutomirski
2019-02-24 15:17 ` Masami Hiramatsu
2019-02-24 17:26 ` Linus Torvalds
2019-02-25 2:40 ` Masami Hiramatsu
2019-02-25 4:49 ` Andy Lutomirski
2019-02-25 8:09 ` Masami Hiramatsu
2019-02-25 16:40 ` Steven Rostedt
2019-02-26 1:35 ` Masami Hiramatsu
2019-02-25 8:33 ` Peter Zijlstra
2019-02-25 14:52 ` Peter Zijlstra
2019-02-25 16:48 ` Kees Cook
2019-02-25 16:58 ` Andy Lutomirski
2019-02-25 17:07 ` Kees Cook
2019-02-21 7:52 ` Masami Hiramatsu
2019-02-21 14:36 ` Steven Rostedt
2019-02-21 15:58 ` Masami Hiramatsu
2019-02-21 16:16 ` Masami Hiramatsu
2019-02-21 16:32 ` Steven Rostedt
2019-02-23 14:48 ` Masami Hiramatsu
2019-02-15 17:47 ` [PATCH 2/2 v2] tracing: Fix number of entries in trace header Steven Rostedt
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