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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: Jann Horn <jannh@google.com>, Nadav Amit <namit@vmware.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Changbin Du <changbin.du@gmail.com>,
	Kees Cook <keescook@chromium.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Network Development <netdev@vger.kernel.org>,
	"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>,
	Dave Hansen <dave.hansen@intel.com>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Igor Stoppa <igor.stoppa@gmail.com>
Subject: Re: [PATCH 1/2 v2] kprobe: Do not use uaccess functions to access kernel memory that can fault
Date: Fri, 22 Feb 2019 16:03:56 -0800	[thread overview]
Message-ID: <20190223000355.wpmku2gu6cg3dklh@ast-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <CALCETrU2V5KBA97g3O-yHiUu1acmM_K9b2a5ATmKSqGwdd-+Dw@mail.gmail.com>

On Fri, Feb 22, 2019 at 03:59:30PM -0800, Andy Lutomirski wrote:
> >
> > A relatively simple approach might be to teach BPF not to run kprobe
> > programs and such in contexts where current->mm isn't the active mm?
> > Maybe using nmi_uaccess_okay(), or something like that? It looks like
> > perf_callchain_user() also already uses that. Except that a lot of
> > this code is x86-specific...
> 
> This sounds like exactly the right solution.  If you're running from
> some unknown context (like NMI or tracing), then you should check
> nmi_uaccess_okay().  I think we should just promote that to be a
> non-arch-specific function (that returns true by default) and check it
> the relevant bpf_probe_xyz() functions.
> 
> Alexei, does that seem reasonable?

yep. I think that should work.


  reply	other threads:[~2019-02-23  0:04 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 [this message]
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
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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