From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Subject: [RFC][PATCH 4/3] vfs: Allow rmdir to remove mounts in all but the current mount namespace Date: Fri, 04 Oct 2013 19:34:49 -0700 Message-ID: <87a9ioo37a.fsf_-_@xmission.com> References: <87a9kkax0j.fsf@xmission.com> <8761v7h2pt.fsf@tw-ebiederman.twitter.com> <87li281wx6.fsf_-_@xmission.com> Mime-Version: 1.0 Content-Type: text/plain Cc: "Serge E. Hallyn" , Al Viro , Linux-Fsdevel , Kernel Mailing List , Andy Lutomirski , Rob Landley , Linus Torvalds To: Miklos Szeredi Return-path: Received: from out01.mta.xmission.com ([166.70.13.231]:34496 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751196Ab3JECfB (ORCPT ); Fri, 4 Oct 2013 22:35:01 -0400 In-Reply-To: <87li281wx6.fsf_-_@xmission.com> (Eric W. Biederman's message of "Fri, 04 Oct 2013 15:41:25 -0700") Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Programs have been known to test for empty directories by attempting to remove them. To keep from violating the principle of least surprise don't let directories the caller can see with someting mounted on them be deleted. With a little luck this may prevent commands stupid commands like rm -rf from eating your system. Signed-off-by: "Eric W. Biederman" --- fs/namei.c | 21 +++++++++++++++++++++ 1 files changed, 21 insertions(+), 0 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index b18b017c946b..b9cae480ac27 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -3547,6 +3547,20 @@ void dentry_unhash(struct dentry *dentry) spin_unlock(&dentry->d_lock); } +static bool covered(struct vfsmount *mnt, struct dentry *dentry) +{ + /* test to see if a dentry is covered with a mount in + * the current mount namespace. + */ + bool is_covered; + + rcu_read_lock(); + is_covered = d_mountpoint(dentry) && __lookup_mnt(mnt, dentry, 1); + rcu_read_unlock(); + + return is_covered; +} + int vfs_rmdir(struct inode *dir, struct dentry *dentry) { int error = may_delete(dir, dentry, 1); @@ -3619,6 +3633,9 @@ retry: error = -ENOENT; goto exit3; } + error = -EBUSY; + if (covered(nd.path.mnt, dentry)) + goto exit3; error = security_path_rmdir(&nd.path, dentry); if (error) goto exit3; @@ -4155,6 +4172,10 @@ retry: error = -ENOTEMPTY; if (new_dentry == trap) goto exit5; + error = -EBUSY; + if (new_dentry->d_inode && S_ISDIR(new_dentry->d_inode->i_mode) && + covered(newnd.path.mnt, new_dentry)) + goto exit5; error = security_path_rename(&oldnd.path, old_dentry, &newnd.path, new_dentry); -- 1.7.5.4