From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754760AbaHALAi (ORCPT ); Fri, 1 Aug 2014 07:00:38 -0400 Received: from mail-we0-f174.google.com ([74.125.82.174]:40644 "EHLO mail-we0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753060AbaHALAh (ORCPT ); Fri, 1 Aug 2014 07:00:37 -0400 Date: Fri, 1 Aug 2014 13:00:29 +0200 From: Ingo Molnar To: Masami Hiramatsu Cc: linux-kernel@vger.kernel.org, Ananth N Mavinakayanahalli , "David S. Miller" Subject: Re: [PATCH -tip ] [BUGFIX] kprobes: Skip kretprobe hit in NMI context to avoid deadlock Message-ID: <20140801110029.GA31286@gmail.com> References: <20140801084254.12330.64728.stgit@kbuild-fedora.novalocal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140801084254.12330.64728.stgit@kbuild-fedora.novalocal> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Masami Hiramatsu wrote: > Skip kretprobe hit in NMI context, because if an NMI happens > inside the critical section protected by kretprobe_table.lock > and another(or same) kretprobe hit, pre_kretprobe_handler > tries to lock kretprobe_table.lock again. > Normal interrupts have no problem because they are disabled > with the lock. > > Signed-off-by: Masami Hiramatsu > Cc: Ananth N Mavinakayanahalli > Cc: "David S. Miller" > --- > kernel/kprobes.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index 734e9a7..a537029 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -1778,6 +1778,12 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs) > unsigned long hash, flags = 0; > struct kretprobe_instance *ri; > > + /* To avoid deadlock, prohibit return probing in NMI context */ > + if (in_nmi()) { Should be unlikely()? > + rp->nmissed++; > + return 0; In another place in this function we do: } else { rp->nmissed++; raw_spin_unlock_irqrestore(&rp->lock, flags); } Is it safe to modify rp-> without locking? > + } > + > /*TODO: consider to only swap the RA after the last pre_handler fired */ Nit: That comment is oddly formatted. Thanks, Ingo