From patchwork Tue Jun 9 10:53:10 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ritesh Harjani X-Patchwork-Id: 11595249 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8CB5B159A for ; Tue, 9 Jun 2020 10:54:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7D8E32078D for ; Tue, 9 Jun 2020 10:54:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728672AbgFIKx5 (ORCPT ); Tue, 9 Jun 2020 06:53:57 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:1250 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728593AbgFIKxj (ORCPT ); Tue, 9 Jun 2020 06:53:39 -0400 Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 059AXCI9107631; Tue, 9 Jun 2020 06:53:20 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 31j59u7yk9-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 09 Jun 2020 06:53:20 -0400 Received: from m0098399.ppops.net (m0098399.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 059AXOf6108484; Tue, 9 Jun 2020 06:53:19 -0400 Received: from ppma03ams.nl.ibm.com (62.31.33a9.ip4.static.sl-reverse.com [169.51.49.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 31j59u7yj1-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 09 Jun 2020 06:53:19 -0400 Received: from pps.filterd (ppma03ams.nl.ibm.com [127.0.0.1]) by ppma03ams.nl.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 059AfOQV013020; Tue, 9 Jun 2020 10:53:17 GMT Received: from b06cxnps3075.portsmouth.uk.ibm.com (d06relay10.portsmouth.uk.ibm.com [9.149.109.195]) by ppma03ams.nl.ibm.com with ESMTP id 31g2s7wsa7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 09 Jun 2020 10:53:17 +0000 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 059ArFaD58851400 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 9 Jun 2020 10:53:15 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0D2DFAE055; Tue, 9 Jun 2020 10:53:15 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 33063AE053; Tue, 9 Jun 2020 10:53:13 +0000 (GMT) Received: from localhost.localdomain.com (unknown [9.199.37.89]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 9 Jun 2020 10:53:13 +0000 (GMT) From: Ritesh Harjani To: linux-ext4@vger.kernel.org Cc: jack@suse.com, tytso@mit.edu, Hillf Danton , linux-fsdevel@vger.kernel.org, Ritesh Harjani , Borislav Petkov , Marek Szyprowski , syzbot+82f324bb69744c5f6969@syzkaller.appspotmail.com Subject: [PATCHv2 1/1] ext4: mballoc: Use this_cpu_read instead of this_cpu_ptr Date: Tue, 9 Jun 2020 16:23:10 +0530 Message-Id: <534f275016296996f54ecf65168bb3392b6f653d.1591699601.git.riteshh@linux.ibm.com> X-Mailer: git-send-email 2.25.4 MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.687 definitions=2020-06-09_03:2020-06-09,2020-06-09 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 lowpriorityscore=0 spamscore=0 impostorscore=0 priorityscore=1501 malwarescore=0 adultscore=0 mlxscore=0 cotscore=-2147483648 phishscore=0 mlxlogscore=907 bulkscore=0 suspectscore=1 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006090081 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Simplify reading a seq variable by directly using this_cpu_read API instead of doing this_cpu_ptr and then dereferencing it. This also avoid the below kernel BUG: which happens when CONFIG_DEBUG_PREEMPT is enabled BUG: using smp_processor_id() in preemptible [00000000] code: syz-fuzzer/6927 caller is ext4_mb_new_blocks+0xa4d/0x3b70 fs/ext4/mballoc.c:4711 CPU: 1 PID: 6927 Comm: syz-fuzzer Not tainted 5.7.0-next-20200602-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+0x18f/0x20d lib/dump_stack.c:118 check_preemption_disabled+0x20d/0x220 lib/smp_processor_id.c:48 ext4_mb_new_blocks+0xa4d/0x3b70 fs/ext4/mballoc.c:4711 ext4_ext_map_blocks+0x201b/0x33e0 fs/ext4/extents.c:4244 ext4_map_blocks+0x4cb/0x1640 fs/ext4/inode.c:626 ext4_getblk+0xad/0x520 fs/ext4/inode.c:833 ext4_bread+0x7c/0x380 fs/ext4/inode.c:883 ext4_append+0x153/0x360 fs/ext4/namei.c:67 ext4_init_new_dir fs/ext4/namei.c:2757 [inline] ext4_mkdir+0x5e0/0xdf0 fs/ext4/namei.c:2802 vfs_mkdir+0x419/0x690 fs/namei.c:3632 do_mkdirat+0x21e/0x280 fs/namei.c:3655 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:359 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fixes: 42f56b7a4a7d ("ext4: mballoc: introduce pcpu seqcnt for freeing PA to improve ENOSPC handling") Suggested-by: Borislav Petkov Tested-by: Marek Szyprowski Signed-off-by: Ritesh Harjani Reported-by: syzbot+82f324bb69744c5f6969@syzkaller.appspotmail.com Reviewed-by: Christoph Hellwig --- fs/ext4/mballoc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index a9083113a8c0..c0a331e2feb0 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -4708,7 +4708,7 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle, } ac->ac_op = EXT4_MB_HISTORY_PREALLOC; - seq = *this_cpu_ptr(&discard_pa_seq); + seq = this_cpu_read(discard_pa_seq); if (!ext4_mb_use_preallocated(ac)) { ac->ac_op = EXT4_MB_HISTORY_ALLOC; ext4_mb_normalize_request(ac, ar);