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=-16.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, USER_AGENT_SANE_1 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 53277C433E6 for ; Tue, 22 Dec 2020 02:00:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 22B5C22A83 for ; Tue, 22 Dec 2020 02:00:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726365AbgLVB7z (ORCPT ); Mon, 21 Dec 2020 20:59:55 -0500 Received: from out30-44.freemail.mail.aliyun.com ([115.124.30.44]:58927 "EHLO out30-44.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726213AbgLVB7z (ORCPT ); Mon, 21 Dec 2020 20:59:55 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R911e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04420;MF=joseph.qi@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0UJOMT.j_1608602350; Received: from B-D1K7ML85-0059.local(mailfrom:joseph.qi@linux.alibaba.com fp:SMTPD_---0UJOMT.j_1608602350) by smtp.aliyun-inc.com(127.0.0.1); Tue, 22 Dec 2020 09:59:10 +0800 Subject: Re: [PATCH v3] ovl: fix dentry leak in ovl_get_redirect To: Liangyan , Al Viro , Miklos Szeredi , linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org References: <20201221183327.134077-1-liangyan.peng@linux.alibaba.com> From: Joseph Qi Message-ID: <5a12fda7-8153-6191-416b-d510c993ce63@linux.alibaba.com> Date: Tue, 22 Dec 2020 09:59:10 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20201221183327.134077-1-liangyan.peng@linux.alibaba.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/22/20 2:33 AM, Liangyan wrote: > We need to lock d_parent->d_lock before dget_dlock, or this may > have d_lockref updated parallelly like calltrace below which will > cause dentry->d_lockref leak and risk a crash. > > CPU 0 CPU 1 > ovl_set_redirect lookup_fast > ovl_get_redirect __d_lookup > dget_dlock > //no lock protection here spin_lock(&dentry->d_lock) > dentry->d_lockref.count++ dentry->d_lockref.count++ > > [   49.799059] PGD 800000061fed7067 P4D 800000061fed7067 PUD 61fec5067 PMD 0 > [   49.799689] Oops: 0002 [#1] SMP PTI > [   49.800019] CPU: 2 PID: 2332 Comm: node Not tainted 4.19.24-7.20.al7.x86_64 #1 > [   49.800678] Hardware name: Alibaba Cloud Alibaba Cloud ECS, BIOS 8a46cfe 04/01/2014 > [   49.801380] RIP: 0010:_raw_spin_lock+0xc/0x20 > [   49.803470] RSP: 0018:ffffac6fc5417e98 EFLAGS: 00010246 > [   49.803949] RAX: 0000000000000000 RBX: ffff93b8da3446c0 RCX: 0000000a00000000 > [   49.804600] RDX: 0000000000000001 RSI: 000000000000000a RDI: 0000000000000088 > [   49.805252] RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff993cf040 > [   49.805898] R10: ffff93b92292e580 R11: ffffd27f188a4b80 R12: 0000000000000000 > [   49.806548] R13: 00000000ffffff9c R14: 00000000fffffffe R15: ffff93b8da3446c0 > [   49.807200] FS:  00007ffbedffb700(0000) GS:ffff93b927880000(0000) knlGS:0000000000000000 > [   49.807935] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [   49.808461] CR2: 0000000000000088 CR3: 00000005e3f74006 CR4: 00000000003606a0 > [   49.809113] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [   49.809758] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [   49.810410] Call Trace: > [   49.810653]  d_delete+0x2c/0xb0 > [   49.810951]  vfs_rmdir+0xfd/0x120 > [   49.811264]  do_rmdir+0x14f/0x1a0 > [   49.811573]  do_syscall_64+0x5b/0x190 > [   49.811917]  entry_SYSCALL_64_after_hwframe+0x44/0xa9 > [   49.812385] RIP: 0033:0x7ffbf505ffd7 > [   49.814404] RSP: 002b:00007ffbedffada8 EFLAGS: 00000297 ORIG_RAX: 0000000000000054 > [   49.815098] RAX: ffffffffffffffda RBX: 00007ffbedffb640 RCX: 00007ffbf505ffd7 > [   49.815744] RDX: 0000000004449700 RSI: 0000000000000000 RDI: 0000000006c8cd50 > [   49.816394] RBP: 00007ffbedffaea0 R08: 0000000000000000 R09: 0000000000017d0b > [   49.817038] R10: 0000000000000000 R11: 0000000000000297 R12: 0000000000000012 > [   49.817687] R13: 00000000072823d8 R14: 00007ffbedffb700 R15: 00000000072823d8 > [   49.818338] Modules linked in: pvpanic cirrusfb button qemu_fw_cfg atkbd libps2 i8042 > [   49.819052] CR2: 0000000000000088 > [   49.819368] ---[ end trace 4e652b8aa299aa2d ]--- > [   49.819796] RIP: 0010:_raw_spin_lock+0xc/0x20 > [   49.821880] RSP: 0018:ffffac6fc5417e98 EFLAGS: 00010246 > [   49.822363] RAX: 0000000000000000 RBX: ffff93b8da3446c0 RCX: 0000000a00000000 > [   49.823008] RDX: 0000000000000001 RSI: 000000000000000a RDI: 0000000000000088 > [   49.823658] RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff993cf040 > [   49.825404] R10: ffff93b92292e580 R11: ffffd27f188a4b80 R12: 0000000000000000 > [   49.827147] R13: 00000000ffffff9c R14: 00000000fffffffe R15: ffff93b8da3446c0 > [   49.828890] FS:  00007ffbedffb700(0000) GS:ffff93b927880000(0000) knlGS:0000000000000000 > [   49.830725] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [   49.832359] CR2: 0000000000000088 CR3: 00000005e3f74006 CR4: 00000000003606a0 > [   49.834085] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [   49.835792] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > Fixes: a6c606551141 ("ovl: redirect on rename-dir") > Signed-off-by: Liangyan > Reviewed-by: Joseph Qi > Suggested-by: Al Viro > --- > fs/overlayfs/dir.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c > index 28a075b5f5b2..e9aa4a12ad82 100644 > --- a/fs/overlayfs/dir.c > +++ b/fs/overlayfs/dir.c > @@ -973,6 +973,7 @@ static char *ovl_get_redirect(struct dentry *dentry, bool abs_redirect) > for (d = dget(dentry); !IS_ROOT(d);) { > const char *name; > int thislen; > + struct dentry *parent = NULL; No need to initialize 'parent' here. > > spin_lock(&d->d_lock); > name = ovl_dentry_get_redirect(d); > @@ -992,11 +993,10 @@ static char *ovl_get_redirect(struct dentry *dentry, bool abs_redirect) > > buflen -= thislen; > memcpy(&buf[buflen], name, thislen); > - tmp = dget_dlock(d->d_parent); 'tmp' won't be used any more, so you'd better clean it up. Thanks, Joseph > spin_unlock(&d->d_lock); > - > + parent = dget_parent(d); > dput(d); > - d = tmp; > + d = parent; > > /* Absolute redirect: finished */ > if (buf[buflen] == '/') >