Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754536AbaDDSvn (ORCPT ); Fri, 4 Apr 2014 14:51:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56145 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754186AbaDDSvi (ORCPT ); Fri, 4 Apr 2014 14:51:38 -0400 Date: Fri, 4 Apr 2014 20:51:39 +0200 From: Oleg Nesterov To: Ingo Molnar , Srikar Dronamraju Cc: Ananth N Mavinakayanahalli , Anton Arapov , David Long , Denys Vlasenko , "Frank Ch. Eigler" , Jim Keniston , Jonathan Lebon , Masami Hiramatsu , linux-kernel@vger.kernel.org Subject: [PATCH v2 8/9] uprobes/x86: Send SIGILL if arch_uprobe_post_xol() fails Message-ID: <20140404185139.GA14753@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140404185038.GA14679@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently the error from arch_uprobe_post_xol() is silently ignored. This doesn't look good and this can lead to the hard-to-debug problems. 1. Change handle_singlestep() to loudly complain and send SIGILL. Note: this only affects x86, ppc/arm can't fail. 2. Change arch_uprobe_post_xol() to call arch_uprobe_abort_xol() and avoid TF games if it is going to return an error. This can help to to analyze the problem, if nothing else we should not report ->ip = xol_slot in the core-file. Note: this means that handle_riprel_post_xol() can be called twice, but this is fine because it is idempotent. Signed-off-by: Oleg Nesterov --- arch/x86/kernel/uprobes.c | 16 ++++++++++++---- kernel/events/uprobes.c | 8 +++++++- 2 files changed, 19 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c index 08cdb82..e72903e 100644 --- a/arch/x86/kernel/uprobes.c +++ b/arch/x86/kernel/uprobes.c @@ -594,6 +594,15 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) struct uprobe_task *utask = current->utask; WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR); + + if (auprobe->ops->post_xol) { + int err = auprobe->ops->post_xol(auprobe, regs); + if (err) { + arch_uprobe_abort_xol(auprobe, regs); + return err; + } + } + current->thread.trap_nr = utask->autask.saved_trap_nr; /* * arch_uprobe_pre_xol() doesn't save the state of TIF_BLOCKSTEP @@ -605,8 +614,6 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) else if (!(auprobe->fixups & UPROBE_FIX_SETF)) regs->flags &= ~X86_EFLAGS_TF; - if (auprobe->ops->post_xol) - return auprobe->ops->post_xol(auprobe, regs); return 0; } @@ -641,8 +648,9 @@ int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, /* * This function gets called when XOL instruction either gets trapped or - * the thread has a fatal signal, so reset the instruction pointer to its - * probed address. + * the thread has a fatal signal, or if arch_uprobe_post_xol() failed. + * Reset the instruction pointer to its probed address for the potential + * restart or for post mortem analysis. */ void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) { diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 7a3e14e..2adbc97 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -1858,10 +1858,11 @@ out: static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs) { struct uprobe *uprobe; + int err = 0; uprobe = utask->active_uprobe; if (utask->state == UTASK_SSTEP_ACK) - arch_uprobe_post_xol(&uprobe->arch, regs); + err = arch_uprobe_post_xol(&uprobe->arch, regs); else if (utask->state == UTASK_SSTEP_TRAPPED) arch_uprobe_abort_xol(&uprobe->arch, regs); else @@ -1875,6 +1876,11 @@ static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs) spin_lock_irq(¤t->sighand->siglock); recalc_sigpending(); /* see uprobe_deny_signal() */ spin_unlock_irq(¤t->sighand->siglock); + + if (unlikely(err)) { + uprobe_warn(current, "execute the probed insn, sending SIGILL."); + force_sig_info(SIGILL, SEND_SIG_FORCED, current); + } } /* -- 1.5.5.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/