linux-kernel - Re: [RFC v6 35/62] powerpc: Deliver SEGV signal on pkey violation

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Message-Id: <20170822180637.GA17106@ram.oc3035372033.ibm.com>
Date:   Tue, 22 Aug 2017 11:06:37 -0700
From:   Ram Pai <linuxram@...ibm.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
        linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
        benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
        khandual@...ux.vnet.ibm.com, aneesh.kumar@...ux.vnet.ibm.com,
        bsingharora@...il.com, dave.hansen@...el.com, hbabu@...ibm.com,
        arnd@...db.de, akpm@...ux-foundation.org, corbet@....net,
        mingo@...hat.com, mhocko@...nel.org
Subject: Re: [RFC v6 35/62] powerpc: Deliver SEGV signal on pkey violation

On Sat, Aug 19, 2017 at 02:09:58PM -0500, Eric W. Biederman wrote:
> Ram Pai <linuxram@...ibm.com> writes:
> 
> > diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> > index d4e545d..fe1e7c7 100644
> > --- a/arch/powerpc/kernel/traps.c
> > +++ b/arch/powerpc/kernel/traps.c
> > @@ -20,6 +20,7 @@
> >  #include <linux/sched/debug.h>
> >  #include <linux/kernel.h>
> >  #include <linux/mm.h>
> > +#include <linux/pkeys.h>
> >  #include <linux/stddef.h>
> >  #include <linux/unistd.h>
> >  #include <linux/ptrace.h>
> > @@ -247,6 +248,15 @@ void user_single_step_siginfo(struct task_struct *tsk,
> >  	info->si_addr = (void __user *)regs->nip;
> >  }
> >  
> > +#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
> > +static void fill_sig_info_pkey(int si_code, siginfo_t *info, unsigned long addr)
> > +{
> > +	if (si_code != SEGV_PKUERR)
> > +		return;
> 
> Given that SEGV_PKUERR is a signal specific si_code this test is
> insufficient to detect an pkey error.  You also need to check
> that signr == SIGSEGV

true. will make it a more precise check.

Thanks
RP