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=-10.8 required=3.0 tests=BAYES_00, FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 81D8AC433F5 for ; Fri, 24 Sep 2021 07:21:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 69AFC60F21 for ; Fri, 24 Sep 2021 07:21:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244320AbhIXHXA convert rfc822-to-8bit (ORCPT ); Fri, 24 Sep 2021 03:23:00 -0400 Received: from n169-111.mail.139.com ([120.232.169.111]:46537 "EHLO n169-111.mail.139.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244191AbhIXHW7 (ORCPT ); Fri, 24 Sep 2021 03:22:59 -0400 X-Greylist: delayed 560 seconds by postgrey-1.27 at vger.kernel.org; Fri, 24 Sep 2021 03:22:59 EDT X-RM-TagInfo: emlType=0 X-RM-SPAM: X-RM-SPAM-FLAG: 00000000 Received: from smtpclient.apple (unknown[59.37.125.124]) by rmsmtp-lg-appmail-16-12015 (RichMail) with SMTP id 2eef614d7a43db7-aacda; Fri, 24 Sep 2021 15:12:04 +0800 (CST) X-RM-TRANSID: 2eef614d7a43db7-aacda Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Mime-Version: 1.0 (1.0) Subject: Re: [PATCH] ovl: fix oops in ovl_rename From: 139 In-Reply-To: <20210924011628.2069334-1-zhengliang6@huawei.com> Date: Fri, 24 Sep 2021 15:12:03 +0800 Cc: miklos@szeredi.hu, linux-unionfs@vger.kernel.org, yi.zhang@huawei.com Message-Id: References: <20210924011628.2069334-1-zhengliang6@huawei.com> To: Zheng Liang X-Mailer: iPhone Mail (18G82) Precedence: bulk List-ID: X-Mailing-List: linux-unionfs@vger.kernel.org 在 2021年9月24日，09:09，Zheng Liang 写道： > > We find a kernel NULL pointer dereference problem in overlayfs. > The problem can appear in the following scene: > > mkdir lower upper work merge > touch lower/old > touch lower/new > mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merge > rm merge/new > ------------------------------------------------------------------------------------------ > process A(rename file in merge) process B(delete file in upper) > renameat2(AT_FDCWD, "old", AT_FDCWD, "new", 0) > (new is whiteout file in upper) > do_renameat2 > vfs_rename > ovl_rename > (overwrite=true,ovl_lower_positive(old)=true, > ovl_dentry_is_whiteout(new)=true) > (we can add some delay after "flags|=RENAME_EXCHANGE", > it can make the problem appear more easy) > …… unlink(new) > …… (delete whiteout in upper) > (newdentry is negative) > ovl_do_rename Is it a real use case? I believe there will be many unexpected behaviors if you delete the files in upper layer deliberately. Thanks, Chengguang > > So,before commencing with ovl_do_rename that the flags maybe attach RENAME_EXCHANGE > and the newdentry is negative in ovl_rename.If we enabled selinux,it > will lead to kernel panic.such as the following log: > PID: 2552045 TASK: ffff8880302faf00 CPU: 2 COMMAND: "fsstress" > #0 [ffff888080e772a0] machine_kexec at ffffffff856adedc > #1 [ffff888080e773a8] __crash_kexec at ffffffff8585cd20 > #2 [ffff888080e774c0] panic at ffffffff8572b288 > #3 [ffff888080e77590] oops_end at ffffffff85641f6e > #4 [ffff888080e775f0] __do_page_fault at ffffffff856cd55b > #5 [ffff888080e77668] do_page_fault at ffffffff856cd834 > #6 [ffff888080e776a0] async_page_fault at ffffffff8660125e > [exception RIP: __inode_security_revalidate+34] > RIP: ffffffff85c43452 RSP: ffff888080e77758 RFLAGS: 00010202 > RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff8593ae7e > RDX: 0000000000000000 RSI: 0000000000000297 RDI: 0000000000000297 > RBP: ffff8881984e6628 R8: ffffed10115e3f39 R9: ffffed10115e3f39 > R10: 0000000000000001 R11: ffffed10115e3f38 R12: 0000000000000001 > R13: 0000000000000000 R14: ffff88808350a000 R15: 1ffff110101ceef5 > ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 > #7 [ffff888080e77780] selinux_inode_rename at ffffffff85c4418d > #8 [ffff888080e77858] security_inode_rename at ffffffff85c35f24 > #9 [ffff888080e77890] vfs_rename at ffffffff85b01209 > #10 [ffff888080e779a8] ovl_do_rename at ffffffffc0a44c22 [overlay] > #11 [ffff888080e779d8] ovl_rename at ffffffffc0a46575 [overlay] > #12 [ffff888080e77b48] vfs_rename at ffffffff85b0155a > #13 [ffff888080e77c60] do_renameat2 at ffffffff85b06e65 > #14 [ffff888080e77f00] __x64_sys_renameat2 at ffffffff85b06fb2 > #15 [ffff888080e77f30] do_syscall_64 at ffffffff85606243 > #16 [ffff888080e77f50] entry_SYSCALL_64_after_hwframe at ffffffff866000ad > > We can add some check in ovl_rename for this scene and return error to avoid kernel panic. > > Signed-off-by: Zheng Liang > --- > fs/overlayfs/dir.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c > index 1fefb2b8960e..93c7c267de93 100644 > --- a/fs/overlayfs/dir.c > +++ b/fs/overlayfs/dir.c > @@ -1219,9 +1219,13 @@ static int ovl_rename(struct user_namespace *mnt_userns, struct inode *olddir, > goto out_dput; > } > } else { > - if (!d_is_negative(newdentry) && > - (!new_opaque || !ovl_is_whiteout(newdentry))) > - goto out_dput; > + if (!d_is_negative(newdentry)) { > + if (!new_opaque || !ovl_is_whiteout(newdentry)) > + goto out_dput; > + } else { > + if (flags & RENAME_EXCHANGE) > + goto out_dput; > + } > } > > if (olddentry == trap) > -- > 2.25.4 >