lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20140403163219.GA4882@linux.vnet.ibm.com>
Date:	Thu, 3 Apr 2014 22:02:19 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	David Long <dave.long@...aro.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	Jonathan Lebon <jlebon@...hat.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/7] uprobes: Kill UPROBE_SKIP_SSTEP and can_skip_sstep()

> UPROBE_COPY_INSN, UPROBE_SKIP_SSTEP, and uprobe->flags must die. This
> patch kills UPROBE_SKIP_SSTEP. I never understood why it was added;
> not only it doesn't help, it harms.
> 
> It can only help to avoid arch_uprobe_skip_sstep() if it was already
> called before and failed. But this is ugly, if we want to know whether
> we can emulate this instruction or not we should do this analysis in
> arch_uprobe_analyze_insn(), not when we hit this probe for the first
> time.
> 
> And in fact this logic is simply wrong. arch_uprobe_skip_sstep() can
> fail or not depending on the task/register state, if this insn can be
> emulated but, say, put_user() fails we need to xol it this time, but
> this doesn't mean we shouldn't try to emulate it when this or another
> thread hist this bp next time.
> 
> And this is the actual reason for this change. We need to emulate the
> "call" insn, but push(return-address) can obviously fail.
> 
> Per-arch notes:
> 
> 	x86: __skip_sstep() can only emulate "rep;nop". With this
> 	     change it will be called every time and most probably
> 	     for no reason.
> 
> 	     This will be fixed by the next changes. We need to
> 	     change this suboptimal code anyway.
> 
> 	arm: Should not be affected. It has its own "bool simulate"
> 	     flag checked in arch_uprobe_skip_sstep().
> 
> 	ppc: Looks like, it can emulate almost everything. Does it
> 	     actually needs to record the fact that emulate_step()
> 	     failed? Hopefully not. But if yes, it can add the ppc-
> 	     specific flag into arch_uprobe.
> 
> TODO: rename arch_uprobe_skip_sstep() to arch_uprobe_emulate_insn(),
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

-- 
Thanks and Regards
Srikar Dronamraju

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ