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=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 94795C4360C for ; Tue, 2 Mar 2021 03:08:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 76A9E61606 for ; Tue, 2 Mar 2021 03:08:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241181AbhCBBpa (ORCPT ); Mon, 1 Mar 2021 20:45:30 -0500 Received: from mail.kernel.org ([198.145.29.99]:46146 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237646AbhCATVp (ORCPT ); Mon, 1 Mar 2021 14:21:45 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 02D1C64FBC; Mon, 1 Mar 2021 17:37:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1614620276; bh=k6vtMchoWGyWtWELp5BGWeV7s51JHBk/vSco0li3SZA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qnvECTT9NR79RhsTo6enY9IYNvZf2pp8Yy4i9ylzHFaOw055BWm/aZOnAj6PnmfQ6 4GVSHcy2P2koSzAKp44b+/EonIaE3goCBxS9rEwBGIVW2/BPhISk3h3VtU75hR5dRv J8dpaigX9TbMX8gZc5hlqFHVRm1t0QqXWFqFrTLU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+3536db46dfa58c573458@syzkaller.appspotmail.com, syzbot+516acdb03d3e27d91bcd@syzkaller.appspotmail.com, Marco Elver , Andrii Nakryiko , Martin KaFai Lau , Sasha Levin Subject: [PATCH 5.11 094/775] bpf_lru_list: Read double-checked variable once without lock Date: Mon, 1 Mar 2021 17:04:22 +0100 Message-Id: <20210301161206.322948484@linuxfoundation.org> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210301161201.679371205@linuxfoundation.org> References: <20210301161201.679371205@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: Marco Elver [ Upstream commit 6df8fb83301d68ea0a0c0e1cbcc790fcc333ed12 ] For double-checked locking in bpf_common_lru_push_free(), node->type is read outside the critical section and then re-checked under the lock. However, concurrent writes to node->type result in data races. For example, the following concurrent access was observed by KCSAN: write to 0xffff88801521bc22 of 1 bytes by task 10038 on cpu 1: __bpf_lru_node_move_in kernel/bpf/bpf_lru_list.c:91 __local_list_flush kernel/bpf/bpf_lru_list.c:298 ... read to 0xffff88801521bc22 of 1 bytes by task 10043 on cpu 0: bpf_common_lru_push_free kernel/bpf/bpf_lru_list.c:507 bpf_lru_push_free kernel/bpf/bpf_lru_list.c:555 ... Fix the data races where node->type is read outside the critical section (for double-checked locking) by marking the access with READ_ONCE() as well as ensuring the variable is only accessed once. Fixes: 3a08c2fd7634 ("bpf: LRU List") Reported-by: syzbot+3536db46dfa58c573458@syzkaller.appspotmail.com Reported-by: syzbot+516acdb03d3e27d91bcd@syzkaller.appspotmail.com Signed-off-by: Marco Elver Signed-off-by: Andrii Nakryiko Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/bpf/20210209112701.3341724-1-elver@google.com Signed-off-by: Sasha Levin --- kernel/bpf/bpf_lru_list.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/kernel/bpf/bpf_lru_list.c b/kernel/bpf/bpf_lru_list.c index 1b6b9349cb857..d99e89f113c43 100644 --- a/kernel/bpf/bpf_lru_list.c +++ b/kernel/bpf/bpf_lru_list.c @@ -502,13 +502,14 @@ struct bpf_lru_node *bpf_lru_pop_free(struct bpf_lru *lru, u32 hash) static void bpf_common_lru_push_free(struct bpf_lru *lru, struct bpf_lru_node *node) { + u8 node_type = READ_ONCE(node->type); unsigned long flags; - if (WARN_ON_ONCE(node->type == BPF_LRU_LIST_T_FREE) || - WARN_ON_ONCE(node->type == BPF_LRU_LOCAL_LIST_T_FREE)) + if (WARN_ON_ONCE(node_type == BPF_LRU_LIST_T_FREE) || + WARN_ON_ONCE(node_type == BPF_LRU_LOCAL_LIST_T_FREE)) return; - if (node->type == BPF_LRU_LOCAL_LIST_T_PENDING) { + if (node_type == BPF_LRU_LOCAL_LIST_T_PENDING) { struct bpf_lru_locallist *loc_l; loc_l = per_cpu_ptr(lru->common_lru.local_list, node->cpu); -- 2.27.0