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=unavailable 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 123B7C433E0 for ; Tue, 23 Jun 2020 17:36:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DCCD82078A for ; Tue, 23 Jun 2020 17:36:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592933793; bh=ixsHUQGYOCZM9ksHuB4vVsBeM8l6i98MFux05+DDgQs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=fePyDq1YmMZRBEWMKf3nmLrxZm7AouxGRCNeT12nu3G0XFeJ4rCTZp5C5iRfzCa0B 3Opk5aAGlkxPc5JOyhurH2xry7WSyXuUTwhzJDJD0/fDrZYTo8mOrnlHQZMlyMI8IA 49jCPjJPO3uojc2om3qh9OyFK5ps7UTcrhXSKfPo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732962AbgFWRgd (ORCPT ); Tue, 23 Jun 2020 13:36:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:33628 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387570AbgFWRg0 (ORCPT ); Tue, 23 Jun 2020 13:36:26 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (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 CA52E20774; Tue, 23 Jun 2020 17:36:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592933785; bh=ixsHUQGYOCZM9ksHuB4vVsBeM8l6i98MFux05+DDgQs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NzdVTN6d5vw1fujIQhviV0blIkhmNHA1Cpu93lP7aAZCN40B0ODA9qoU1EX62JOoa 1YZKgYXJjRixMZB/G2VX7v01Ix3/YypIfjjZnnal3eMqkNrlZN9PtNpHN1nfJafaym SyNCeDU1Q8KLfQPgyarUmS+UPP2zYSDsAVRlc4dc= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Masami Hiramatsu , Anders Roxell , Joel Fernandes , Steven Rostedt , Sasha Levin Subject: [PATCH AUTOSEL 5.4 21/24] kprobes: Suppress the suspicious RCU warning on kprobes Date: Tue, 23 Jun 2020 13:35:56 -0400 Message-Id: <20200623173559.1355728-21-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200623173559.1355728-1-sashal@kernel.org> References: <20200623173559.1355728-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Masami Hiramatsu [ Upstream commit 6743ad432ec92e680cd0d9db86cb17b949cf5a43 ] Anders reported that the lockdep warns that suspicious RCU list usage in register_kprobe() (detected by CONFIG_PROVE_RCU_LIST.) This is because get_kprobe() access kprobe_table[] by hlist_for_each_entry_rcu() without rcu_read_lock. If we call get_kprobe() from the breakpoint handler context, it is run with preempt disabled, so this is not a problem. But in other cases, instead of rcu_read_lock(), we locks kprobe_mutex so that the kprobe_table[] is not updated. So, current code is safe, but still not good from the view point of RCU. Joel suggested that we can silent that warning by passing lockdep_is_held() to the last argument of hlist_for_each_entry_rcu(). Add lockdep_is_held(&kprobe_mutex) at the end of the hlist_for_each_entry_rcu() to suppress the warning. Link: http://lkml.kernel.org/r/158927055350.27680.10261450713467997503.stgit@devnote2 Reported-by: Anders Roxell Suggested-by: Joel Fernandes Reviewed-by: Joel Fernandes (Google) Signed-off-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Sasha Levin --- kernel/kprobes.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 2625c241ac00f..bd484392d7894 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -326,7 +326,8 @@ struct kprobe *get_kprobe(void *addr) struct kprobe *p; head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)]; - hlist_for_each_entry_rcu(p, head, hlist) { + hlist_for_each_entry_rcu(p, head, hlist, + lockdep_is_held(&kprobe_mutex)) { if (p->addr == addr) return p; } -- 2.25.1