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=-8.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 9D234C433DF for ; Fri, 5 Jun 2020 11:29:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 76A0C2053B for ; Fri, 5 Jun 2020 11:29:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="CG8N5gSk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726302AbgFEL30 (ORCPT ); Fri, 5 Jun 2020 07:29:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50278 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725997AbgFEL3Z (ORCPT ); Fri, 5 Jun 2020 07:29:25 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AA78BC08C5C2; Fri, 5 Jun 2020 04:29:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=rZem03oAMdNWUhBZ6CZrdIFIDXPK1/y9NBQ0iiUcplQ=; b=CG8N5gSksZQ3f+8Oa2Z+u1lkF4 4dwK4SW3Sx+8CLV/jpXCx6DkCpe4oz5V7rz8eekwF2gKnc5xKvUyU+WOsKXro4hlMI1KATqv0CcUc Y2kpb7XBEVLhKK0TVRD49MMwQiHhT4M2hAkCv12f3KFHCNCWXu+A+xG8QqS2WiHba1Qs8dD3ZMJjU 0iGgOc2sw/V9mafQakFKd1DsDrSZx5BpSuTkK6Dd9xtz3LMZVJ+T3bO6xnYJkxMhAp+xtc1AdEPx9 B86GSu803akmnw8krXCJE5p5tZOtn5r4SjoxPh71ObZUwUgaWiWdCzeknhnYPJsMW9T4WfH4tHqej AfdfGllg==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jhAXK-00034v-3B; Fri, 05 Jun 2020 11:29:22 +0000 Date: Fri, 5 Jun 2020 04:29:22 -0700 From: Matthew Wilcox To: Eric Biggers Cc: syzbot , bjorn.andersson@linaro.org, davem@davemloft.net, kuba@kernel.org, linux-kernel@vger.kernel.org, manivannan.sadhasivam@linaro.org, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: BUG: using smp_processor_id() in preemptible code in radix_tree_node_alloc Message-ID: <20200605112922.GB19604@bombadil.infradead.org> References: <000000000000a363b205a74ca6a2@google.com> <20200605035555.GA2667@sol.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200605035555.GA2667@sol.localdomain> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Jun 04, 2020 at 08:55:55PM -0700, Eric Biggers wrote: > Possibly a bug in lib/radix-tree.c? this_cpu_ptr() in radix_tree_node_alloc() > can be reached without a prior preempt_disable(). Or is the caller of > idr_alloc() doing something wrong? Yes, the idr_alloc() call is plainly wrong: mutex_lock(&qrtr_port_lock); if (!*port) { rc = idr_alloc(&qrtr_ports, ipc, QRTR_MIN_EPH_SOCKET, QRTR_MAX_EPH_SOCKET + 1, GFP_ATOMIC); If we can take a mutex lock, there's no excuse to be using GFP_ATOMIC. That (and the call slightly lower in the function) should be GFP_KERNEL as the minimal fix (below). I'll send a followup patch which converts this IDR to the XArray instead. diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c index 2d8d6131bc5f..d2547711d20c 100644 --- a/net/qrtr/qrtr.c +++ b/net/qrtr/qrtr.c @@ -692,15 +692,15 @@ static int qrtr_port_assign(struct qrtr_sock *ipc, int *port) if (!*port) { rc = idr_alloc(&qrtr_ports, ipc, QRTR_MIN_EPH_SOCKET, QRTR_MAX_EPH_SOCKET + 1, - GFP_ATOMIC); + GFP_KERNEL); if (rc >= 0) *port = rc; } else if (*port < QRTR_MIN_EPH_SOCKET && !capable(CAP_NET_ADMIN)) { rc = -EACCES; } else if (*port == QRTR_PORT_CTRL) { - rc = idr_alloc(&qrtr_ports, ipc, 0, 1, GFP_ATOMIC); + rc = idr_alloc(&qrtr_ports, ipc, 0, 1, GFP_KERNEL); } else { - rc = idr_alloc(&qrtr_ports, ipc, *port, *port + 1, GFP_ATOMIC); + rc = idr_alloc(&qrtr_ports, ipc, *port, *port + 1, GFP_KERNEL); if (rc >= 0) *port = rc; } > On Thu, Jun 04, 2020 at 07:02:18PM -0700, syzbot wrote: > > Hello, > > > > syzbot found the following crash on: > > > > HEAD commit: acf25aa6 Merge tag 'Smack-for-5.8' of git://github.com/csc.. > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=13d6307a100000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=5263d9b5bce03c67 > > dashboard link: https://syzkaller.appspot.com/bug?extid=3eec59e770685e3dc879 > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15bd4c1e100000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1520c9de100000 > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+3eec59e770685e3dc879@syzkaller.appspotmail.com > > > > RAX: ffffffffffffffda RBX: 00007ffdf01d56d0 RCX: 00000000004406c9 > > RDX: 0000000000000000 RSI: 0000000020000240 RDI: 0000000000000003 > > RBP: 0000000000000005 R08: 0000000000000001 R09: 0000000000000031 > > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401f50 > > R13: 0000000000401fe0 R14: 0000000000000000 R15: 0000000000000000 > > BUG: using smp_processor_id() in preemptible [00000000] code: syz-executor036/6796 > > caller is radix_tree_node_alloc.constprop.0+0x200/0x330 lib/radix-tree.c:262 > > CPU: 0 PID: 6796 Comm: syz-executor036 Not tainted 5.7.0-syzkaller #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > Call Trace: > > __dump_stack lib/dump_stack.c:77 [inline] > > dump_stack+0x188/0x20d lib/dump_stack.c:118 > > check_preemption_disabled lib/smp_processor_id.c:47 [inline] > > debug_smp_processor_id.cold+0x88/0x9b lib/smp_processor_id.c:57 > > radix_tree_node_alloc.constprop.0+0x200/0x330 lib/radix-tree.c:262 > > radix_tree_extend+0x256/0x4e0 lib/radix-tree.c:424 > > idr_get_free+0x60c/0x8e0 lib/radix-tree.c:1492 > > idr_alloc_u32+0x170/0x2d0 lib/idr.c:46 > > idr_alloc+0xc2/0x130 lib/idr.c:87 > > qrtr_port_assign net/qrtr/qrtr.c:703 [inline] > > __qrtr_bind.isra.0+0x12e/0x5c0 net/qrtr/qrtr.c:756 > > qrtr_autobind net/qrtr/qrtr.c:787 [inline] > > qrtr_autobind+0xaf/0xf0 net/qrtr/qrtr.c:775 > > qrtr_sendmsg+0x1d6/0x770 net/qrtr/qrtr.c:895 > > sock_sendmsg_nosec net/socket.c:652 [inline] > > sock_sendmsg+0xcf/0x120 net/socket.c:672 > > ____sys_sendmsg+0x6e6/0x810 net/socket.c:2352 > > ___sys_sendmsg+0x100/0x170 net/socket.c:2406 > > __sys_sendmsg+0xe5/0x1b0 net/socket.c:2439 > > do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 > > entry_SYSCALL_64_after_hwframe+0x49/0xb3 > > RIP: 0033:0x4406c9 > > Code: 25 02 00 85 c0 b8 00 00 00 00 48 0f 44 c3 5b c3 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00 > > RSP: 002b:00007ffdf01d56c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e > > RAX: ffffffffffffffda RBX: 00007ffdf01d56d0 RCX: 00000000004406c9 > > RDX: 0000000000000000 RSI: 0000000020000240 RDI: 0000000000000003 > > RBP: 0000000000000005 R08: 0000000000000001 R09: 0000000000000031 > > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401f50 > > R13: 0000000000401fe0 R14: 0000000000000000 R15: 0000000000000000 > > > > > > --- > > This bug is generated by a bot. It may contain errors. > > See https://goo.gl/tpsmEJ for more information about syzbot. > > syzbot engineers can be reached at syzkaller@googlegroups.com. > > > > syzbot will keep track of this bug report. See: > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > syzbot can test patches for this bug, for details see: > > https://goo.gl/tpsmEJ#testing-patches > >