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From: Steven Rostedt <rostedt@goodmis.org>
To: Alexander Popov <alex.popov@linux.com>
Cc: kernel-hardening@lists.openwall.com,
	Kees Cook <keescook@chromium.org>, Jann Horn <jannh@google.com>,
	Ingo Molnar <mingo@kernel.org>, Andy Lutomirski <luto@kernel.org>,
	Joerg Roedel <joro@8bytes.org>, Borislav Petkov <bp@alien8.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Peter Zijlstra <peterz@infradead.org>, Jan Kara <jack@suse.cz>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] stackleak: Disable ftrace for stackleak.c
Date: Sun, 11 Nov 2018 20:53:51 -0500	[thread overview]
Message-ID: <20181111205351.1874bb1e@vmware.local.home> (raw)
In-Reply-To: <eeb7f5ee-1e2e-d37b-cca2-e0a29826e8eb@linux.com>

On Sun, 11 Nov 2018 13:19:45 +0300
Alexander Popov <alex.popov@linux.com> wrote:

> On 11.11.2018 2:30, Steven Rostedt wrote:
> > On Sun, 11 Nov 2018 01:05:30 +0300
> > Alexander Popov <alex.popov@linux.com> wrote:
> >   
> >> The stackleak_erase() function is called on the trampoline stack at the
> >> end of syscall. This stack is not big enough for ftrace operations,
> >> e.g. it can be overflowed if we enable kprobe_events for stackleak_erase().  
> > 
> > Is the issue with kprobes or with function tracing? Because this stops
> > function tracing which I only want disabled if function tracing itself
> > is an issue, not for other things that may use the function tracing
> > infrastructure.  
> 
> Hello Steven,
> 
> I believe that stackleak erasing is not compatible with function tracing itself.
> That's what the kernel testing robot has hit:
> https://www.openwall.com/lists/kernel-hardening/2018/11/09/1
> 
> I used kprobe_events just to reproduce the problem:
> https://www.openwall.com/lists/kernel-hardening/2018/11/09/4

Have you tried adding a "notrace" to stackleak_erase()?

Not tracing the entire file is a bit of overkill. There's no reason
ftrace can't trace stack_erasing_sysctl() or perhaps even
stackleak_track_stack() as that may be very interesting to trace.

-- Steve

  reply	other threads:[~2018-11-12  1:53 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-10 22:05 [PATCH 1/1] stackleak: Disable ftrace for stackleak.c Alexander Popov
2018-11-10 23:30 ` Steven Rostedt
2018-11-11 10:19   ` Alexander Popov
2018-11-12  1:53     ` Steven Rostedt [this message]
2018-11-12  2:50       ` Masami Hiramatsu
2018-11-12 14:53         ` Mathieu Desnoyers
2018-11-12 16:52           ` Steven Rostedt
2018-11-12 16:51         ` Alexander Popov
2018-11-12 17:21           ` Steven Rostedt
2018-11-13 18:21             ` Masami Hiramatsu

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