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=-9.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT 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 D3CAAC43387 for ; Thu, 17 Jan 2019 13:47:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9F1DA20855 for ; Thu, 17 Jan 2019 13:47:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547732872; bh=4UuTzWWNP2NvSrP2pjQo0hgPvFgdpQUrValRB2065FM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=jKlMqOnyVd1JcD54lE1kyNroG1So7Bd5zWSLN9E+BXNWRHWJE7Os+Eyh26xoAMHLG Fs/cDnI46Qa4GR4Wg6Zg7HRt/njLi2s3Hhk75LL0ydISbvcIRAOpx/56u8i/pF5iQw xlwx96aKYmjx2L/m1/3WwtZGdn/2n+4xXmEFHfD0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726805AbfAQNrv (ORCPT ); Thu, 17 Jan 2019 08:47:51 -0500 Received: from mail.kernel.org ([198.145.29.99]:42836 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725889AbfAQNru (ORCPT ); Thu, 17 Jan 2019 08:47:50 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (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 B69DA20851; Thu, 17 Jan 2019 13:47:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547732869; bh=4UuTzWWNP2NvSrP2pjQo0hgPvFgdpQUrValRB2065FM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=i0JGkFzDf3aYsrugasNoI4a5gtbq3HaZdVpu5e0uLwkqyg/eyJjl6IbMkAYoPBF0B rrOGVTQzgSmEgfR+tNSvKTNC3ONgPg7sXOR7huubGCDtkdSAkn2Rn8JrOSkK2a2MyB MlNxbGBaAYcnxf6c9yCAXJGLsUwC6Xe5SYyiIP+g= Date: Thu, 17 Jan 2019 14:47:46 +0100 From: Greg Kroah-Hartman To: Andreas Ziegler Cc: Masami Hiramatsu , Steven Rostedt , Ingo Molnar , "linux-kernel@vger.kernel.org" Subject: Re: uprobes: bug in comm/string output? Message-ID: <20190117134746.GA12542@kroah.com> References: <8b67136d-28d7-a734-6366-9511e30d66a7@fau.de> <20190116190054.ac22c8495540578834446236@kernel.org> <62276858-9135-2393-8993-64e1088db7b9@fau.de> <20190117151309.711d41ebdd761b525a168837@kernel.org> <20190117170015.403157bf619907f8467189fe@kernel.org> <17147ef5-4348-9a02-d781-0f089fe603f5@fau.de> <20190117184717.9bbd1218b9f4fe6a8070a0fe@kernel.org> <15ce335e-d40e-f9ef-e85a-507e153c55cb@fau.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <15ce335e-d40e-f9ef-e85a-507e153c55cb@fau.de> User-Agent: Mutt/1.11.2 (2019-01-07) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 17, 2019 at 02:44:41PM +0100, Andreas Ziegler wrote: > Hi, > > On 1/17/19 10:47 AM, Masami Hiramatsu wrote: > > On Thu, 17 Jan 2019 09:08:41 +0100 > > Andreas Ziegler wrote: > > > > > On 17.01.19 09:00, Masami Hiramatsu wrote: > > > > On Thu, 17 Jan 2019 15:13:09 +0900 > > > > Masami Hiramatsu wrote: > > > > > > > > > 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. > > > > > > this should read 're-enables'. > > > > > > > > > > > > > For $comm support, use strncpy() instead of strncpy_from_user() > > > ^ > > > we're using strlcpy(), not strncpy(). > > > > > > > > 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 > > > ^ ^ > > > 'uses', and the function should be 'strnlen_user()'. > > > > > > > > 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); > > > > > > > > To balance with the strnlen_user, we must increse the len in this block. > > > > (strlen doesn't count the final '\0', but strnlen_user counts it) > > > > > > > > > > yes, we need to add a '+ 1' here. > > > > > > With the typos and this one fixed, this is > > > > > > Acked-by: Andreas Ziegler > > > > Thank you for fixing typo and Ack :) > > > > Thanks you, > > > > > > > > > Thank you, > > > > > > > > > + 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; > > > > > > > > > > > > > > > > as the original commit breaking $comm support was merged for v4.20 (which is > a stable kernel) and the wrong behaviour with multiple strings exists in all > longterm/stable releases (tested back to v4.4), do you think this should be > going into a stable release once it's merged? > > I added Greg as he might know the answer to that. Sounds like it would be a patch to be backported to the stable kernels to me. greg k-h