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[23.128.96.18]) by mx.google.com with ESMTP id oj15si432621pjb.149.2022.01.24.13.16.44; Mon, 24 Jan 2022 13:16:57 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@linuxfoundation.org header.s=korg header.b=B9L6SHnh; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linuxfoundation.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1389465AbiAXUk5 (ORCPT + 99 others); Mon, 24 Jan 2022 15:40:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35632 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1380962AbiAXUVD (ORCPT ); Mon, 24 Jan 2022 15:21:03 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 085CFC0604F4; Mon, 24 Jan 2022 11:39:15 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id C2DDFB8119D; Mon, 24 Jan 2022 19:39:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 05E65C340E5; Mon, 24 Jan 2022 19:39:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643053152; bh=5EYbqNegLlvnaMSWowG9UrcVkePTyeevdZP3O7Ejjos=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=B9L6SHnhjIaVty7CSqSBh0+m3W329XeDNf8wxjSwf32EFpqktRK78ECOE+Yo1jqcc QbfI4uysB6zAntRqiKUQ6w8dqQVxt+C+rJxzHZuP8t3B1sNupynuAW9J6DtzArmiw8 AWwQbCtf7Ds0C89dSr7DtfFp8uSSzPXAIWSfQdiQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , syzbot , Jakub Kicinski Subject: [PATCH 5.4 293/320] af_unix: annote lockless accesses to unix_tot_inflight & gc_in_progress Date: Mon, 24 Jan 2022 19:44:37 +0100 Message-Id: <20220124184003.909210029@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220124183953.750177707@linuxfoundation.org> References: <20220124183953.750177707@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: Eric Dumazet commit 9d6d7f1cb67cdee15f1a0e85aacfb924e0e02435 upstream. wait_for_unix_gc() reads unix_tot_inflight & gc_in_progress without synchronization. Adds READ_ONCE()/WRITE_ONCE() and their associated comments to better document the intent. BUG: KCSAN: data-race in unix_inflight / wait_for_unix_gc write to 0xffffffff86e2b7c0 of 4 bytes by task 9380 on cpu 0: unix_inflight+0x1e8/0x260 net/unix/scm.c:63 unix_attach_fds+0x10c/0x1e0 net/unix/scm.c:121 unix_scm_to_skb net/unix/af_unix.c:1674 [inline] unix_dgram_sendmsg+0x679/0x16b0 net/unix/af_unix.c:1817 unix_seqpacket_sendmsg+0xcc/0x110 net/unix/af_unix.c:2258 sock_sendmsg_nosec net/socket.c:704 [inline] sock_sendmsg net/socket.c:724 [inline] ____sys_sendmsg+0x39a/0x510 net/socket.c:2409 ___sys_sendmsg net/socket.c:2463 [inline] __sys_sendmmsg+0x267/0x4c0 net/socket.c:2549 __do_sys_sendmmsg net/socket.c:2578 [inline] __se_sys_sendmmsg net/socket.c:2575 [inline] __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2575 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae read to 0xffffffff86e2b7c0 of 4 bytes by task 9375 on cpu 1: wait_for_unix_gc+0x24/0x160 net/unix/garbage.c:196 unix_dgram_sendmsg+0x8e/0x16b0 net/unix/af_unix.c:1772 unix_seqpacket_sendmsg+0xcc/0x110 net/unix/af_unix.c:2258 sock_sendmsg_nosec net/socket.c:704 [inline] sock_sendmsg net/socket.c:724 [inline] ____sys_sendmsg+0x39a/0x510 net/socket.c:2409 ___sys_sendmsg net/socket.c:2463 [inline] __sys_sendmmsg+0x267/0x4c0 net/socket.c:2549 __do_sys_sendmmsg net/socket.c:2578 [inline] __se_sys_sendmmsg net/socket.c:2575 [inline] __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2575 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae value changed: 0x00000002 -> 0x00000004 Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 9375 Comm: syz-executor.1 Not tainted 5.16.0-rc7-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Fixes: 9915672d4127 ("af_unix: limit unix_tot_inflight") Signed-off-by: Eric Dumazet Reported-by: syzbot Link: https://lore.kernel.org/r/20220114164328.2038499-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/unix/garbage.c | 14 +++++++++++--- net/unix/scm.c | 6 ++++-- 2 files changed, 15 insertions(+), 5 deletions(-) --- a/net/unix/garbage.c +++ b/net/unix/garbage.c @@ -192,8 +192,11 @@ void wait_for_unix_gc(void) { /* If number of inflight sockets is insane, * force a garbage collect right now. + * Paired with the WRITE_ONCE() in unix_inflight(), + * unix_notinflight() and gc_in_progress(). */ - if (unix_tot_inflight > UNIX_INFLIGHT_TRIGGER_GC && !gc_in_progress) + if (READ_ONCE(unix_tot_inflight) > UNIX_INFLIGHT_TRIGGER_GC && + !READ_ONCE(gc_in_progress)) unix_gc(); wait_event(unix_gc_wait, gc_in_progress == false); } @@ -213,7 +216,9 @@ void unix_gc(void) if (gc_in_progress) goto out; - gc_in_progress = true; + /* Paired with READ_ONCE() in wait_for_unix_gc(). */ + WRITE_ONCE(gc_in_progress, true); + /* First, select candidates for garbage collection. Only * in-flight sockets are considered, and from those only ones * which don't have any external reference. @@ -299,7 +304,10 @@ void unix_gc(void) /* All candidates should have been detached by now. */ BUG_ON(!list_empty(&gc_candidates)); - gc_in_progress = false; + + /* Paired with READ_ONCE() in wait_for_unix_gc(). */ + WRITE_ONCE(gc_in_progress, false); + wake_up(&unix_gc_wait); out: --- a/net/unix/scm.c +++ b/net/unix/scm.c @@ -59,7 +59,8 @@ void unix_inflight(struct user_struct *u } else { BUG_ON(list_empty(&u->link)); } - unix_tot_inflight++; + /* Paired with READ_ONCE() in wait_for_unix_gc() */ + WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + 1); } user->unix_inflight++; spin_unlock(&unix_gc_lock); @@ -79,7 +80,8 @@ void unix_notinflight(struct user_struct if (atomic_long_dec_and_test(&u->inflight)) list_del_init(&u->link); - unix_tot_inflight--; + /* Paired with READ_ONCE() in wait_for_unix_gc() */ + WRITE_ONCE(unix_tot_inflight, unix_tot_inflight - 1); } user->unix_inflight--; spin_unlock(&unix_gc_lock);