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Message-ID: <55148B9E.1070203@intel.com>
Date: Thu, 26 Mar 2015 15:43:42 -0700
From: Dave Hansen <dave.hansen@intel.com>
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To: "Yu, Fenghua" <fenghua.yu@intel.com>, Oleg Nesterov <oleg@redhat.com>,
        Borislav Petkov <bp@suse.de>
CC: Quentin Casasnovas <quentin.casasnovas@oracle.com>,
        Andy Lutomirski <luto@amacapital.net>, Ingo Molnar <mingo@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Pekka Riikonen <priikone@iki.fi>, Rik van Riel <riel@redhat.com>,
        Suresh Siddha <sbsiddha@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: Oops with tip/x86/fpu
References: <54F74F59.5070107@intel.com> <20150304190651.GA5589@redhat.com> <20150304200612.GO3663@pd.tnic> <20150305151442.GA18996@redhat.com> <20150305182203.GA4203@redhat.com> <3E5A0FA7E9CA944F9D5414FEC6C712205C8ABDB0@ORSMSX105.amr.corp.intel.com>
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On 03/26/2015 03:37 PM, Yu, Fenghua wrote:
>> > void sighup(int sig, siginfo_t *info, void *ctxt) {
>> > 	struct ucontext *uctxt = ctxt;
>> > 	struct sigcontext *sctxt = (void*)&uctxt->uc_mcontext;
>> > 
>> > 	printf("SIGHUP! %p\n", sctxt->fpstate);
>> > 	sctxt->fpstate = (void *)1;
> sctxt->fpstate=(void *)1 changes the fpstate pointer in the sigcontext. It will generate segfault and bad frame info in kernel.
> 
> This is expected behavior, right? Is this still a valid test?

Just to be clear, I saw a full-on kernel panic induced from an
unprivileged application.

Are you seeing something different?