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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 82ACCC432C0 for ; Wed, 27 Nov 2019 05:57:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 51D9120835 for ; Wed, 27 Nov 2019 05:57:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574834232; bh=2LCywgeMJXg7y4ZWRrSFYRw5cDi6k86r0DUii6K/vjQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=CMlD3AV5rI4TrH2RgwALyrSd/csJc1OmpUyY3YwWQ0EbTF0/A5BQNe1DgtKMm6SX5 zKr9huoUNYVPxEztcICpZh5swmc1gvpzjE6mdAjZ1ualMXgbgezLm1kZY2ruTMRTIF nVLTZqO1tiwmSK75aR9pK7FRwfh38mphuQoIJ/1w= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726873AbfK0F5L (ORCPT ); Wed, 27 Nov 2019 00:57:11 -0500 Received: from mail.kernel.org ([198.145.29.99]:57974 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726558AbfK0F5K (ORCPT ); Wed, 27 Nov 2019 00:57:10 -0500 Received: from localhost.localdomain (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B9799207DD; Wed, 27 Nov 2019 05:57:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574834229; bh=2LCywgeMJXg7y4ZWRrSFYRw5cDi6k86r0DUii6K/vjQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GVK6QVOleKWWTwSsGfvWyZAUIusPFRz9VktM8OyoBWN1OZx/DBMYBzLXgMJn7yrKp ZbqPznc9YfnfDMmHPFDlye1kkp6egzAmsPNYHweuE+uQvG7e6FHnbG+HZ2LtVwnlgE 3FD1LbKAuTdFdsTiS7MxvzFkjqCr3sIduLM0jeRo= From: Masami Hiramatsu To: Ingo Molnar Cc: Steven Rostedt , Peter Zijlstra , x86@kernel.org, linux-kernel@vger.kernel.org, bristot@redhat.com, jbaron@akamai.com, torvalds@linux-foundation.org, tglx@linutronix.de, namit@vmware.com, hpa@zytor.com, luto@kernel.org, ard.biesheuvel@linaro.org, jpoimboe@redhat.com, jeyu@kernel.org, alexei.starovoitov@gmail.com, Masami Hiramatsu Subject: [PATCH -tip 2/2] kprobes: Set unoptimized flag after unoptimizing code Date: Wed, 27 Nov 2019 14:57:04 +0900 Message-Id: <157483422375.25881.13508326028469515760.stgit@devnote2> X-Mailer: git-send-email 2.20.1 In-Reply-To: <157483420094.25881.9190014521050510942.stgit@devnote2> References: <157483420094.25881.9190014521050510942.stgit@devnote2> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Fix to set unoptimized flag after confirming the code is completely unoptimized. Without this fix, when a kprobe hits the intermediate modified instruction (the first byte is replaced by int3, but latter bytes still be a jump address operand) while unoptimizing, it can return to the middle byte of the modified code. And it causes an invalid instruction exception in the kernel. Usually, this is a rare case, but if we put a probe on the function called while text patching, it always causes a kernel panic as below. (text_poke() is used for patching the code in optprobe) # echo p text_poke+5 > kprobe_events # echo 1 > events/kprobes/enable # echo 0 > events/kprobes/enable invalid opcode: 0000 [#1] PREEMPT SMP PTI CPU: 7 PID: 137 Comm: kworker/7:1 Not tainted 5.4.0-rc8+ #29 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014 Workqueue: events kprobe_optimizer RIP: 0010:text_poke+0x9/0x50 Code: 01 00 00 5b 5d 41 5c 41 5d c3 89 c0 0f b7 4c 02 fe 66 89 4c 05 fe e9 31 ff ff ff e8 71 ac 03 00 90 55 48 89 f5 53 cc 30 cb fd <1e> ec 08 8b 05 72 98 31 01 85 c0 75 11 48 83 c4 08 48 89 ee 48 89 RSP: 0018:ffffc90000343df0 EFLAGS: 00010686 RAX: 0000000000000000 RBX: ffffffff81025796 RCX: 0000000000000000 RDX: 0000000000000004 RSI: ffff88807c983148 RDI: ffffffff81025796 RBP: ffff88807c983148 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff82284fe0 R13: ffff88807c983138 R14: ffffffff82284ff0 R15: 0ffff88807d9eee0 FS: 0000000000000000(0000) GS:ffff88807d9c0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000000058158b CR3: 000000007b372000 CR4: 00000000000006a0 Call Trace: arch_unoptimize_kprobe+0x22/0x28 arch_unoptimize_kprobes+0x39/0x87 kprobe_optimizer+0x6e/0x290 process_one_work+0x2a0/0x610 worker_thread+0x28/0x3d0 ? process_one_work+0x610/0x610 kthread+0x10d/0x130 ? kthread_park+0x80/0x80 ret_from_fork+0x3a/0x50 Modules linked in: ---[ end trace 83b34b22a228711b ]--- This can happen even if we blacklist text_poke() and other functions, because there is a small time window which showing the intermediate code to other CPUs. Fixes: 6274de4984a6 ("kprobes: Support delayed unoptimizing") Signed-off-by: Masami Hiramatsu --- kernel/kprobes.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 53534aa258a6..34e28b236d68 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -510,6 +510,8 @@ static void do_unoptimize_kprobes(void) arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list); /* Loop free_list for disarming */ list_for_each_entry_safe(op, tmp, &freeing_list, list) { + /* Switching from detour code to origin */ + op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED; /* Disarm probes if marked disabled */ if (kprobe_disabled(&op->kp)) arch_disarm_kprobe(&op->kp); @@ -649,6 +651,7 @@ static void force_unoptimize_kprobe(struct optimized_kprobe *op) { lockdep_assert_cpus_held(); arch_unoptimize_kprobe(op); + op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED; if (kprobe_disabled(&op->kp)) arch_disarm_kprobe(&op->kp); } @@ -676,7 +679,6 @@ static void unoptimize_kprobe(struct kprobe *p, bool force) return; } - op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED; if (!list_empty(&op->list)) { /* Dequeue from the optimization queue */ list_del_init(&op->list);