From: Cyril Hrubis <chrubis@suse.cz>
To: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Alexandre Chartre <alexandre.chartre@oracle.com>,
kernel test robot <rong.a.chen@intel.com>,
LKML <linux-kernel@vger.kernel.org>,
lkp@lists.01.org, Thomas Gleixner <tglx@linutronix.de>,
ltp@lists.linux.it
Subject: Re: [LTP] [x86/entry] 2bbc68f837: ltp.ptrace08.fail
Date: Wed, 12 Aug 2020 11:31:14 +0200 [thread overview]
Message-ID: <20200812093114.GA13676@yuki.lan> (raw)
In-Reply-To: <CALCETrVX=wxRrv0qw-Enbyg5CEQsy5TigbNt7sSs=MDO6uAnMw@mail.gmail.com>
Hi!
> do_debug is a bit of a red herring here. ptrace should not be able to
> put a breakpoint on a kernel address, period. I would just pick a
> fixed address that's in the kernel text range or even just in the
> pre-KASLR text range and make sure it gets rejected. Maybe try a few
> different addresses for good measure.
I've looked at the code and it seems like this would be a bit more
complicated since the breakpoint is set by an accident in a race and the
call still fails. Which is why the test triggers the breakpoint and
causes infinite loop in the kernel...
I guess that we could instead read back the address with
PTRACE_PEEKUSER, so something as:
break_addr = ptrace(PTRACE_PEEKUSER, child_pid,
(void *)offsetof(struct user, u_debugreg[0]),
NULL);
if (break_addr == kernel_addr)
tst_res(TFAIL, "ptrace() set break on a kernel address");
--
Cyril Hrubis
chrubis@suse.cz
next prev parent reply other threads:[~2020-08-12 9:30 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200616075533.GL5653@shao2-debian>
2020-06-16 8:44 ` [x86/entry] 2bbc68f837: ltp.ptrace08.fail Thomas Gleixner
2020-06-16 12:24 ` [LKP] " Rong Chen
[not found] ` <8E41B15F-D567-4C52-94E9-367015480345@amacapital.net>
2020-06-16 13:27 ` Peter Zijlstra
2020-06-17 13:17 ` [LTP] " Cyril Hrubis
2020-06-18 18:20 ` Andy Lutomirski
2020-08-12 9:31 ` Cyril Hrubis [this message]
2020-08-14 14:58 ` Cyril Hrubis
2020-08-14 16:42 ` Andy Lutomirski
2020-06-18 20:02 ` Thomas Gleixner
2020-06-22 10:16 ` [LKP] " Naresh Kamboju
2020-06-16 14:57 ` Thomas Gleixner
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