From patchwork Tue Sep 29 11:01:21 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 291140 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 81411C4741F for ; Tue, 29 Sep 2020 11:36:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 485D923B6A for ; Tue, 29 Sep 2020 11:36:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601379398; bh=AX49AqUWxqDdiLUL4AeKCNNJi1j2/uulrraP8hlwN88=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=UALL1wa14iZDAc/KXHmfHR6+UiWncomxuPIAB9Pz9BQ8spUqZ95Rt/FZcPtmdStDq gP+I0U1wPEtgmk+PEjetZledHYr6j+NeGj+MVvzYi3tvPGrqJoA1YunW/0TYYB5OGz tyVLzbvTTGh1+gCmGqIT2O7yIq1OTDWAqrWGSGtU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729678AbgI2Lgh (ORCPT ); Tue, 29 Sep 2020 07:36:37 -0400 Received: from mail.kernel.org ([198.145.29.99]:49122 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729901AbgI2Lft (ORCPT ); Tue, 29 Sep 2020 07:35:49 -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 6621123A75; Tue, 29 Sep 2020 11:30:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601379034; bh=AX49AqUWxqDdiLUL4AeKCNNJi1j2/uulrraP8hlwN88=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NnSkMWUQNztV5mueLQSOwQnP3tS16LWGJnFm3G4Kl+hEkUqlJUZpEhUc+P0+tyhuN dEeJwTOvEkJEvwKtKvWE70zlnwtPzINE+Qj105LpzbsG73Cx5RbbhBcJnwwaIXeK5N glyO3TorM0TrU/sZFcM8oPl6n9wtkygmN3ocHVJc= 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 4.19 230/245] bpf: Fix a rcu warning for bpffs map pretty-print Date: Tue, 29 Sep 2020 13:01:21 +0200 Message-Id: <20200929105958.179604950@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200929105946.978650816@linuxfoundation.org> References: <20200929105946.978650816@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@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 c04815bb15cc1..11fade89c1f38 100644 --- a/kernel/bpf/inode.c +++ b/kernel/bpf/inode.c @@ -207,10 +207,12 @@ 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; }