From: Thomas Gleixner <tglx@linutronix.de>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.org>,
Eiichi Tsukata <devel@etsukata.com>,
edwintorok@gmail.com, mingo@redhat.com, bp@alien8.de,
hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org,
Josh Poimboeuf <jpoimboe@redhat.com>,
Joel Fernandes <joel@joelfernandes.org>
Subject: Re: [PATCH] x86/stacktrace: Do not access user space memory unnecessarily
Date: Sat, 20 Jul 2019 10:44:59 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.1907201044150.1782@nanos.tec.linutronix.de> (raw)
In-Reply-To: <alpine.DEB.2.21.1907200039110.1782@nanos.tec.linutronix.de>
On Sat, 20 Jul 2019, Thomas Gleixner wrote:
> On Sat, 20 Jul 2019, Thomas Gleixner wrote:
> > On Fri, 19 Jul 2019, Sean Christopherson wrote:
> > > [ 0.680477] Run /sbin/init as init process
> > > [ 0.682116] init[1]: segfault at 2926a7ef ip 00007f98a49d9c30 sp 00007fffd83e6af0 error 14 in ld-2.23.so[7f98a49d9000+26000]
> >
> > That's because the call into the context tracking muck clobbers RDX which
> > contains the CR2 value on pagefault. So the pagefault resolves to crap and
> > kills init.
> >
> > Brute force fix below. That needs to be conditional on read_cr2 but for now
> > it does the job.
>
> But it does it just for the context tracking case. TRACE_IRQS_OFF* will do
> the same damage.
Hmm, should not becasue that calls through the thunk which preserves RDX.
next prev parent reply other threads:[~2019-07-20 8:46 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-02 5:31 [PATCH] x86/stacktrace: Do not access user space memory unnecessarily Eiichi Tsukata
2019-07-02 7:28 ` Peter Zijlstra
2019-07-02 14:14 ` Thomas Gleixner
2019-07-02 15:33 ` Steven Rostedt
2019-07-02 17:39 ` Steven Rostedt
2019-07-02 17:47 ` Steven Rostedt
2019-07-02 20:18 ` Peter Zijlstra
2019-07-02 20:33 ` Steven Rostedt
2019-07-02 22:02 ` Peter Zijlstra
2019-07-19 20:28 ` Sean Christopherson
2019-07-19 22:23 ` Thomas Gleixner
2019-07-19 23:01 ` Thomas Gleixner
2019-07-20 8:44 ` Thomas Gleixner [this message]
2019-07-20 8:56 ` [PATCH] x86/entry/64: Prevent clobbering of saved CR2 value Thomas Gleixner
2019-07-20 11:20 ` Peter Zijlstra
2019-07-20 12:34 ` [tip:x86/urgent] " tip-bot for Thomas Gleixner
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