From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752648AbaESSlz (ORCPT ); Mon, 19 May 2014 14:41:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51584 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751254AbaESSly (ORCPT ); Mon, 19 May 2014 14:41:54 -0400 Date: Mon, 19 May 2014 20:40:54 +0200 From: Oleg Nesterov To: Ingo Molnar Cc: Denys Vlasenko , Hugh Dickins , Peter Zijlstra , Srikar Dronamraju , linux-kernel@vger.kernel.org Subject: [PATCH] uprobes: Shift ->readpage check from __copy_insn() to uprobe_register() Message-ID: <20140519184054.GA6750@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 Sorry for double-posting, but it seems that this patch didn't reach lkml. Let me resend it just on case. Plus another patch in reply, on top of this change. ------------------------------------------------------------------------------- Subject: [PATCH] uprobes: Shift ->readpage check from __copy_insn() to uprobe_register() copy_insn() fails with -EIO if ->readpage == NULL, but this error is not propagated unless uprobe_register() path finds ->mm which already mmaps this file. In this case (say) "perf record" does not actually install the probe, but the user can't know about this. Move this check into uprobe_register() so that this problem can be detected earlier and reported to user. Note: this is still not perfect, - copy_insn() and arch_uprobe_analyze_insn() should be called by uprobe_register() but this is not simple, we need vm_file for read_mapping_page() (although perhaps we can pass NULL), and we need ->mm for is_64bit_mm() (although this logic is broken anyway). - uprobe_register() should be called by create_trace_uprobe(), not by probe_event_enable(), so that an error can be detected at "perf probe -x" time. This also needs more changes in the core uprobe code, uprobe register/unregister interface was poorly designed from the very beginning. Reported-by: Denys Vlasenko Signed-off-by: Oleg Nesterov --- kernel/events/uprobes.c | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 3b02c72..c56b13e 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -536,9 +536,6 @@ static int __copy_insn(struct address_space *mapping, struct file *filp, void *insn, int nbytes, loff_t offset) { struct page *page; - - if (!mapping->a_ops->readpage) - return -EIO; /* * Ensure that the page that has the original instruction is * populated and in page-cache. @@ -879,6 +876,9 @@ int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer * if (!uc->handler && !uc->ret_handler) return -EINVAL; + /* copy_insn()->read_mapping_page() needs ->readpage() */ + if (!inode->i_mapping->a_ops->readpage) + return -EIO; /* Racy, just to catch the obvious mistakes */ if (offset > i_size_read(inode)) return -EINVAL; -- 1.5.5.1