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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH 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 36307C4321D for ; Fri, 24 Aug 2018 07:57:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CF01A21581 for ; Fri, 24 Aug 2018 07:57:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="z02xthgD" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CF01A21581 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728020AbeHXLav (ORCPT ); Fri, 24 Aug 2018 07:30:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:58144 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727444AbeHXLav (ORCPT ); Fri, 24 Aug 2018 07:30:51 -0400 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 2B8C22157F; Fri, 24 Aug 2018 07:57:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1535097443; bh=p54TBY9+sjRzRX7kw2ugqNKXMV2OA5tqoUAvBJrDqf8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=z02xthgD0SNIyL7gxnrzd14fk/9Gu678Cu37gwokNFvbIqts6Q0sfQvaX+dj+4/oa FDLcIhtEd/h3B+NYnm+kIk9C1/W7E37Kz/TpueDOJTW86DlewDJV2zIaG4IxQnMBCy acSH+i9P0VAcKbyZC6QSCES6lWdQLlACuBK3B1qg= Date: Fri, 24 Aug 2018 16:57:19 +0900 From: Masami Hiramatsu To: Steven Rostedt Cc: Ingo Molnar , Ravi Bangoria , Arnaldo Carvalho de Melo , Michael Rodin , linux-kernel@vger.kernel.org Subject: Re: [BUGFIX PATCH -tip] kprobes/x86: Fix to copy RIP relative instruction correctly Message-Id: <20180824165719.77d1d624d629ad3907dbb55c@kernel.org> In-Reply-To: <20180823214109.5b8f5756@vmware.local.home> References: <153504457253.22602.1314289671019919596.stgit@devbox> <20180823214109.5b8f5756@vmware.local.home> 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 Thu, 23 Aug 2018 21:41:09 -0400 Steven Rostedt wrote: > On Fri, 24 Aug 2018 02:16:12 +0900 > Masami Hiramatsu wrote: > > > Dump of assembler code from 0xffffffffa000207a to 0xffffffffa00020ea: > > 54 push %rsp > > ... > > 48 83 c4 08 add $0x8,%rsp > > 9d popfq > > 48 89 f0 mov %rsi,%rax > > 8b 35 82 7d db e2 mov -0x1d24827e(%rip),%esi > > # 0xffffffff82db9e67 > > > > As it shows, the 2nd mov accesses *(nr_cpu_ids+3) instead of > > *nr_cpu_ids. This leads a kernel freeze because cpumask_next() > > always returns 0 and for_each_cpu() never ended. > > Ouch! Nice catch. > > > > > Fixing this by adding len correctly to real RIP address while > > copying. > > > > Fixes: 63fef14fc98a ("kprobes/x86: Make insn buffer always ROX and use text_poke()") > > Reported-by: Michael Rodin > > Signed-off-by: Masami Hiramatsu > > Cc: stable@vger.kernel.org > > --- > > arch/x86/kernel/kprobes/opt.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c > > index eaf02f2e7300..e92672b8b490 100644 > > --- a/arch/x86/kernel/kprobes/opt.c > > +++ b/arch/x86/kernel/kprobes/opt.c > > @@ -189,7 +189,8 @@ static int copy_optimized_instructions(u8 *dest, u8 *src, u8 *real) > > int len = 0, ret; > > > > while (len < RELATIVEJUMP_SIZE) { > > - ret = __copy_instruction(dest + len, src + len, real, &insn); > > + ret = __copy_instruction(dest + len, src + len, real + len, > > + &insn); > > if (!ret || !can_boost(&insn, src + len)) > > return -EINVAL; > > len += ret; > > Looking at the change that broke this we have: > > > -static int copy_optimized_instructions(u8 *dest, u8 *src) > > +static int copy_optimized_instructions(u8 *dest, u8 *src, u8 *real) > > { > > struct insn insn; > > int len = 0, ret; > > > > while (len < RELATIVEJUMP_SIZE) { > > - ret = __copy_instruction(dest + len, src + len, &insn); > > + ret = __copy_instruction(dest + len, src + len, real, &insn); > > Where "real" was added as a parameter to __copy_instruction. Note that > we pass in "dest + len" but not "real + len" as you patch fixes. > __copy_instruction was changed by the bad commit with: > > > -int __copy_instruction(u8 *dest, u8 *src, struct insn *insn) > > +int __copy_instruction(u8 *dest, u8 *src, u8 *real, struct insn *insn) > > { > > kprobe_opcode_t buf[MAX_INSN_SIZE]; > > unsigned long recovered_insn = > > @@ -387,11 +388,11 @@ int __copy_instruction(u8 *dest, u8 *src, struct insn *insn) > > * have given. > > */ > > newdisp = (u8 *) src + (s64) insn->displacement.value > > - - (u8 *) dest; > > + - (u8 *) real; > > "real" replaces "dest", which was the first parameter to __copy_instruction. > > > return 0; > > And: > > > int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, > > struct kprobe *__unused) > > { > > - u8 *buf; > > - int ret; > > + u8 *buf = NULL, *slot; > > + int ret, len; > > long rel; > > > > if (!can_optimize((unsigned long)op->kp.addr)) > > return -EILSEQ; > > > > - op->optinsn.insn = get_optinsn_slot(); > > - if (!op->optinsn.insn) > > + buf = kzalloc(MAX_OPTINSN_SIZE, GFP_KERNEL); > > + if (!buf) > > return -ENOMEM; > > > > + op->optinsn.insn = slot = get_optinsn_slot(); > > + if (!slot) { > > + ret = -ENOMEM; > > + goto out; > > + } > > + > > /* > > * Verify if the address gap is in 2GB range, because this uses > > * a relative jump. > > */ > > - rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE; > > + rel = (long)slot - (long)op->kp.addr + RELATIVEJUMP_SIZE; > > if (abs(rel) > 0x7fffffff) { > > - __arch_remove_optimized_kprobe(op, 0); > > - return -ERANGE; > > + ret = -ERANGE; > > + goto err; > > } > > > > - buf = (u8 *)op->optinsn.insn; > > "slot" is equivalent to the old "buf". > > > - set_memory_rw((unsigned long)buf & PAGE_MASK, 1); > > + /* Copy arch-dep-instance from template */ > > + memcpy(buf, &optprobe_template_entry, TMPL_END_IDX); > > > > /* Copy instructions into the out-of-line buffer */ > > - ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr); > > - if (ret < 0) { > > - __arch_remove_optimized_kprobe(op, 0); > > - return ret; > > - } > > + ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr, > > + slot + TMPL_END_IDX); > > We pass in "real" as "slot + TMPL_END_IDX" and "dest" as "buf + > TMPL_END_IDX", thus to make it be equivalent to the code before this > commit, "real" should have "+ len" added to it in order to be > equivalent to what was there before. Right! The broken commit splits trampoline buffer into "temporary" destination buffer and "real" trampoline buffer, and use the "real" address for RIP-relative adjustment. However, I forgot to introduce update the "real" address in the copying loop. > > That said... > > Reviewed-by: Steven Rostedt (VMware) Thanks! -- Masami Hiramatsu