From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752532Ab2HBKFb (ORCPT ); Thu, 2 Aug 2012 06:05:31 -0400 Received: from e2.ny.us.ibm.com ([32.97.182.142]:41575 "EHLO e2.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750734Ab2HBKFa (ORCPT ); Thu, 2 Aug 2012 06:05:30 -0400 Date: Thu, 2 Aug 2012 15:35:15 +0530 From: Srikar Dronamraju To: Oleg Nesterov Cc: Ingo Molnar , Anton Arapov , "Frank Ch. Eigler" , Peter Zijlstra , William Cohen , linux-kernel@vger.kernel.org Subject: [PATCH] uprobes: Ignore unsupported instructions in uprobe_mmap Message-ID: <20120802100515.GC5782@linux.vnet.ibm.com> Reply-To: Srikar Dronamraju References: <20120728163157.GA22719@redhat.com> <20120731064730.GB5087@linux.vnet.ibm.com> <20120731124805.GA485@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20120731124805.GA485@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12080210-5112-0000-0000-00000AA7710E Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org uprobe_mmap()->install_breakpoint() can fail if the probed insn is not supported (remember, uprobe_register() succeeds if nobody mmaps inode/offset). Failure in uprobe_mmap() causes mmap_region/do_fork to fail too. However failing mmap_region()/do_fork() because of a probe on an unsupported instruction is wrong. Hence change uprobe_mmap() to ignore unsupported instructions. Oleg Nesterov analyzed the root cause of this problem. While at it, add a missing put_uprobe() in the path where uprobe_mmap() races with uprobe_unregister(). Reported-by: William Cohen Signed-off-by: Srikar Dronamraju Cc: Oleg Nesterov Cc: # v3.5 --- kernel/events/uprobes.c | 13 ++++++++++++- 1 files changed, 12 insertions(+), 1 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index c08a22d..c8a8c39 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -1051,8 +1051,10 @@ int uprobe_mmap(struct vm_area_struct *vma) if (ret == -EEXIST) { ret = 0; - if (!is_swbp_at_addr(vma->vm_mm, vaddr)) + if (!is_swbp_at_addr(vma->vm_mm, vaddr)) { + put_uprobe(uprobe); continue; + } /* * Unable to insert a breakpoint, but @@ -1060,6 +1062,15 @@ int uprobe_mmap(struct vm_area_struct *vma) * probe count. */ atomic_inc(&vma->vm_mm->uprobes_state.count); + } else if (ret == -ENOTSUPP) { + /* + * A probe at unsupported instruction + * shouldnt cause mmap_region() / do_fork() + * to fail. + */ + ret = 0; + put_uprobe(uprobe); + continue; } if (!ret)