From patchwork Mon Mar 29 07:58:05 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 411528 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=-19.0 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, 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 A4FBFC433E1 for ; Mon, 29 Mar 2021 08:15:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 585D3619BA for ; Mon, 29 Mar 2021 08:15:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232170AbhC2IPH (ORCPT ); Mon, 29 Mar 2021 04:15:07 -0400 Received: from mail.kernel.org ([198.145.29.99]:57848 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232704AbhC2INo (ORCPT ); Mon, 29 Mar 2021 04:13:44 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 07148619D4; Mon, 29 Mar 2021 08:13:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1617005619; bh=0zUDoc+wPY9j5AqycS282QWZ0wNBQ6ee7nXyR6ZOi2k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rC+2E/VShCYoP+4mEZpKJpZUn5KbCFF2aSmw+iOYV7lXn05Ks+FVV/IWIElR+TEMd OUui21XkvjZ1PmIDDPPodnasTMUPF+EEO16UnEkICSHGJYiokzfAALXqmKofoQY8Lp ofeB7RTTjV25P1FTW6nyMFA2MORQ2ML0HXktfQv0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot , Wei Wang , David Ahern , Ido Schimmel , Petr Machata , Eric Dumazet , Ido Schimmel , "David S. Miller" , Sasha Levin Subject: [PATCH 5.4 057/111] ipv6: fix suspecious RCU usage warning Date: Mon, 29 Mar 2021 09:58:05 +0200 Message-Id: <20210329075617.105197711@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210329075615.186199980@linuxfoundation.org> References: <20210329075615.186199980@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Wei Wang [ Upstream commit 28259bac7f1dde06d8ba324e222bbec9d4e92f2b ] Syzbot reported the suspecious RCU usage in nexthop_fib6_nh() when called from ipv6_route_seq_show(). The reason is ipv6_route_seq_start() calls rcu_read_lock_bh(), while nexthop_fib6_nh() calls rcu_dereference_rtnl(). The fix proposed is to add a variant of nexthop_fib6_nh() to use rcu_dereference_bh_rtnl() for ipv6_route_seq_show(). The reported trace is as follows: ./include/net/nexthop.h:416 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 2 locks held by syz-executor.0/17895: at: seq_read+0x71/0x12a0 fs/seq_file.c:169 at: seq_file_net include/linux/seq_file_net.h:19 [inline] at: ipv6_route_seq_start+0xaf/0x300 net/ipv6/ip6_fib.c:2616 stack backtrace: CPU: 1 PID: 17895 Comm: syz-executor.0 Not tainted 4.15.0-syzkaller #0 Call Trace: [] __dump_stack lib/dump_stack.c:17 [inline] [] dump_stack+0xd8/0x147 lib/dump_stack.c:53 [] lockdep_rcu_suspicious+0x153/0x15d kernel/locking/lockdep.c:5745 [] nexthop_fib6_nh include/net/nexthop.h:416 [inline] [] ipv6_route_native_seq_show net/ipv6/ip6_fib.c:2488 [inline] [] ipv6_route_seq_show+0x436/0x7a0 net/ipv6/ip6_fib.c:2673 [] seq_read+0xccf/0x12a0 fs/seq_file.c:276 [] proc_reg_read+0x10c/0x1d0 fs/proc/inode.c:231 [] do_loop_readv_writev fs/read_write.c:714 [inline] [] do_loop_readv_writev fs/read_write.c:701 [inline] [] do_iter_read+0x49e/0x660 fs/read_write.c:935 [] vfs_readv+0xfb/0x170 fs/read_write.c:997 [] kernel_readv fs/splice.c:361 [inline] [] default_file_splice_read+0x487/0x9c0 fs/splice.c:416 [] do_splice_to+0x129/0x190 fs/splice.c:879 [] splice_direct_to_actor+0x256/0x890 fs/splice.c:951 [] do_splice_direct+0x1dd/0x2b0 fs/splice.c:1060 [] do_sendfile+0x597/0xce0 fs/read_write.c:1459 [] SYSC_sendfile64 fs/read_write.c:1520 [inline] [] SyS_sendfile64+0x155/0x170 fs/read_write.c:1506 [] do_syscall_64+0x1ff/0x310 arch/x86/entry/common.c:305 [] entry_SYSCALL_64_after_hwframe+0x42/0xb7 Fixes: f88d8ea67fbdb ("ipv6: Plumb support for nexthop object in a fib6_info") Reported-by: syzbot Signed-off-by: Wei Wang Cc: David Ahern Cc: Ido Schimmel Cc: Petr Machata Cc: Eric Dumazet Reviewed-by: Ido Schimmel Reviewed-by: David Ahern Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- include/net/nexthop.h | 24 ++++++++++++++++++++++++ net/ipv6/ip6_fib.c | 2 +- 2 files changed, 25 insertions(+), 1 deletion(-) diff --git a/include/net/nexthop.h b/include/net/nexthop.h index 3bb618e5ecf7..18a5aca26476 100644 --- a/include/net/nexthop.h +++ b/include/net/nexthop.h @@ -291,6 +291,7 @@ static inline struct fib_nh *fib_info_nh(struct fib_info *fi, int nhsel) int fib6_check_nexthop(struct nexthop *nh, struct fib6_config *cfg, struct netlink_ext_ack *extack); +/* Caller should either hold rcu_read_lock(), or RTNL. */ static inline struct fib6_nh *nexthop_fib6_nh(struct nexthop *nh) { struct nh_info *nhi; @@ -311,6 +312,29 @@ static inline struct fib6_nh *nexthop_fib6_nh(struct nexthop *nh) return NULL; } +/* Variant of nexthop_fib6_nh(). + * Caller should either hold rcu_read_lock_bh(), or RTNL. + */ +static inline struct fib6_nh *nexthop_fib6_nh_bh(struct nexthop *nh) +{ + struct nh_info *nhi; + + if (nh->is_group) { + struct nh_group *nh_grp; + + nh_grp = rcu_dereference_bh_rtnl(nh->nh_grp); + nh = nexthop_mpath_select(nh_grp, 0); + if (!nh) + return NULL; + } + + nhi = rcu_dereference_bh_rtnl(nh->nh_info); + if (nhi->family == AF_INET6) + return &nhi->fib6_nh; + + return NULL; +} + static inline struct net_device *fib6_info_nh_dev(struct fib6_info *f6i) { struct fib6_nh *fib6_nh; diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c index 906ac5e6d96c..bb68290ad68d 100644 --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -2382,7 +2382,7 @@ static int ipv6_route_seq_show(struct seq_file *seq, void *v) const struct net_device *dev; if (rt->nh) - fib6_nh = nexthop_fib6_nh(rt->nh); + fib6_nh = nexthop_fib6_nh_bh(rt->nh); seq_printf(seq, "%pi6 %02x ", &rt->fib6_dst.addr, rt->fib6_dst.plen);