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=-13.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 58521C4741F for ; Tue, 29 Sep 2020 11:52:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 133902065C for ; Tue, 29 Sep 2020 11:52:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601380343; bh=sEpzjWuZ9hyjjnZIWEtMkLj3DA6JgKVB0ZbEBx9Bd9I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=xeteFbVbrDFWSZ0n20XndUF9BL5TaO+KhMpil/ansJOeSZcf4aNiHm8a0Gn3Mun8a ZJnxhPN0JEHC1ZfZDEVl5vaTS6dBuCpCJi2NxPkdPSfBuflySZUFmcSCzIyaRPm3Yh OnOqa0cgWOAma4By4JH6xCV3gykcGK5+Z4BFzni8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731096AbgI2LwW (ORCPT ); Tue, 29 Sep 2020 07:52:22 -0400 Received: from mail.kernel.org ([198.145.29.99]:49692 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730976AbgI2Lrt (ORCPT ); Tue, 29 Sep 2020 07:47:49 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (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 BC235206E5; Tue, 29 Sep 2020 11:47:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601380069; bh=sEpzjWuZ9hyjjnZIWEtMkLj3DA6JgKVB0ZbEBx9Bd9I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TdH1vEG6Vw3GPCOw9VUdsvfXA0/k2L2Td57ioFXt39Dvt356d3bv/Y4sAn8bPbw1V 3VcGuTeUPXakHuExPvHLKKdNwoD1TG15CRfcOkoX0zjbOd3HliZnI3a2lJ8DVx0Mwg BKYDb9KdJg6OuOYirWHzxrYQ/fIn8d2I7AfhrBfM= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alexei Starovoitov , Yonghong Song , Andrii Nakryiko , Martin KaFai Lau , Sasha Levin Subject: [PATCH 5.8 52/99] bpf: Fix a rcu warning for bpffs map pretty-print Date: Tue, 29 Sep 2020 13:01:35 +0200 Message-Id: <20200929105932.288309635@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200929105929.719230296@linuxfoundation.org> References: <20200929105929.719230296@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yonghong Song [ Upstream commit ce880cb825fcc22d4e39046a6c3a3a7f6603883d ] Running selftest ./btf_btf -p the kernel had the following warning: [ 51.528185] WARNING: CPU: 3 PID: 1756 at kernel/bpf/hashtab.c:717 htab_map_get_next_key+0x2eb/0x300 [ 51.529217] Modules linked in: [ 51.529583] CPU: 3 PID: 1756 Comm: test_btf Not tainted 5.9.0-rc1+ #878 [ 51.530346] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.el7.centos 04/01/2014 [ 51.531410] RIP: 0010:htab_map_get_next_key+0x2eb/0x300 ... [ 51.542826] Call Trace: [ 51.543119] map_seq_next+0x53/0x80 [ 51.543528] seq_read+0x263/0x400 [ 51.543932] vfs_read+0xad/0x1c0 [ 51.544311] ksys_read+0x5f/0xe0 [ 51.544689] do_syscall_64+0x33/0x40 [ 51.545116] entry_SYSCALL_64_after_hwframe+0x44/0xa9 The related source code in kernel/bpf/hashtab.c: 709 static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key) 710 { 711 struct bpf_htab *htab = container_of(map, struct bpf_htab, map); 712 struct hlist_nulls_head *head; 713 struct htab_elem *l, *next_l; 714 u32 hash, key_size; 715 int i = 0; 716 717 WARN_ON_ONCE(!rcu_read_lock_held()); In kernel/bpf/inode.c, bpffs map pretty print calls map->ops->map_get_next_key() without holding a rcu_read_lock(), hence causing the above warning. To fix the issue, just surrounding map->ops->map_get_next_key() with rcu read lock. Fixes: a26ca7c982cb ("bpf: btf: Add pretty print support to the basic arraymap") Reported-by: Alexei Starovoitov Signed-off-by: Yonghong Song Signed-off-by: Alexei Starovoitov Acked-by: Andrii Nakryiko Cc: Martin KaFai Lau Link: https://lore.kernel.org/bpf/20200916004401.146277-1-yhs@fb.com Signed-off-by: Sasha Levin --- kernel/bpf/inode.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c index fb878ba3f22f0..18f4969552ac2 100644 --- a/kernel/bpf/inode.c +++ b/kernel/bpf/inode.c @@ -226,10 +226,12 @@ static void *map_seq_next(struct seq_file *m, void *v, loff_t *pos) else prev_key = key; + rcu_read_lock(); if (map->ops->map_get_next_key(map, prev_key, key)) { map_iter(m)->done = true; - return NULL; + key = NULL; } + rcu_read_unlock(); return key; } -- 2.25.1