From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 17566C43387 for ; Thu, 17 Jan 2019 06:13:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D8EF220854 for ; Thu, 17 Jan 2019 06:13:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547705594; bh=VO92TbOWj9bd+RmcAOwk08LEpgVxgeYGe8/ku+rPKAk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=WRczLpDHaalM5JQ6GgezKzAHSCbw9Z6ObXfDRNqjl/1XeGANLx/BtUDDmnk4O40Vv 8J7mixfwzlH7NvXdperTkoxjapOxOHT84dH3E9c731ibH2ZcAkdiSaXXhtt5fkZNy6 YQw3zurbVKp6+w5dU/dEGyzklasD4cZLES9u9k1I= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730006AbfAQGNN (ORCPT ); Thu, 17 Jan 2019 01:13:13 -0500 Received: from mail.kernel.org ([198.145.29.99]:44396 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725320AbfAQGNM (ORCPT ); Thu, 17 Jan 2019 01:13:12 -0500 Received: from devbox (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9FE4C20851; Thu, 17 Jan 2019 06:13:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547705591; bh=VO92TbOWj9bd+RmcAOwk08LEpgVxgeYGe8/ku+rPKAk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=1ToW7rRhy2s8r4OZY0Pn2r3cCvqKBXNBqPMCdIO/u3n9LKG+56PC7XmUFCb6/renY P8NvC26zRJsYpzDC7AccaCVPzE7mODvsUU2XLdg6o4Nh4ho3wB+y23otQq0qrUTMpX M43BlTpVOBTh+QfJ994KjqnyJLo75ZM/Sp+uEE08= Date: Thu, 17 Jan 2019 15:13:09 +0900 From: Masami Hiramatsu To: Andreas Ziegler Cc: Steven Rostedt , Ingo Molnar , "linux-kernel@vger.kernel.org" Subject: Re: uprobes: bug in comm/string output? Message-Id: <20190117151309.711d41ebdd761b525a168837@kernel.org> In-Reply-To: <62276858-9135-2393-8993-64e1088db7b9@fau.de> References: <8b67136d-28d7-a734-6366-9511e30d66a7@fau.de> <20190116190054.ac22c8495540578834446236@kernel.org> <62276858-9135-2393-8993-64e1088db7b9@fau.de> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 16 Jan 2019 11:16:07 +0100 Andreas Ziegler wrote: > > I went into this a bit deeper today, and right now it is simply failing > to parse the code because there is no FETCH_OP_COMM case in > process_fetch_insn() for uprobes so that will return -EILSEQ, leading to > a make_data_loc(0, ...) in store_trace_args(). If we just add > FETCH_OP_COMM and let val point to current->comm (that's what > trace_kprobe.c does), we get an -EFAULT return value from > fetch_store_string because strncpy_from_user() checks if the argument is > in user space. Correct. I missed to add OP_COMM support. And uprobe's fetch_store_string is only for user space strings. > So I think we might need a special case for that, something like > FETCH_OP_ST_COMM_STRING which is only used for FETCH_OP_COMM and copies > current->comm over to the dynamic area. The implementation could be > similar to the old fetch_comm_string implementation before your rewrite. Hmm, instead, I would like to add current->comm checker and only allows to copy that. That would be simpler and enough. Could you test below patch? tracing: uprobes: Re-enable $comm support for uprobe events From: Masami Hiramatsu Since commit 533059281ee5 ("tracing: probeevent: Introduce new argument fetching code") dropped the $comm support from uprobe events, this re-enable it. For $comm support, use strncpy() instead of strncpy_from_user() to copy current task's comm. Because it is in the kernel space, strncpy_from_user() always fails to copy the comm. This also use strlen() instead of strlen_user() to measure the length of the comm. Signed-off-by: Masami Hiramatsu Reported-by: Andreas Ziegler --- kernel/trace/trace_uprobe.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index e335576b9411..97d134e83e0f 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -156,7 +156,10 @@ fetch_store_string(unsigned long addr, void *dest, void *base) if (unlikely(!maxlen)) return -ENOMEM; - ret = strncpy_from_user(dst, src, maxlen); + if (addr == (unsigned long)current->comm) + ret = strlcpy(dst, current->comm, maxlen); + else + ret = strncpy_from_user(dst, src, maxlen); if (ret >= 0) { if (ret == maxlen) dst[ret - 1] = '\0'; @@ -173,7 +176,10 @@ fetch_store_strlen(unsigned long addr) int len; void __user *vaddr = (void __force __user *) addr; - len = strnlen_user(vaddr, MAX_STRING_SIZE); + if (addr == (unsigned long)current->comm) + len = strlen(current->comm); + else + len = strnlen_user(vaddr, MAX_STRING_SIZE); return (len > MAX_STRING_SIZE) ? 0 : len; } @@ -213,6 +219,9 @@ process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs, void *dest, case FETCH_OP_IMM: val = code->immediate; break; + case FETCH_OP_COMM: + val = (unsigned long)current->comm; + break; case FETCH_OP_FOFFS: val = translate_user_vaddr(code->immediate); break;