From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Kent Subject: [RFC PATCH 6/8] autofs - use path_is_mountpoint() to fix unreliable d_mountpoint() checks Date: Mon, 03 Oct 2016 08:46:54 +0800 Message-ID: <20161003004654.4865.8095.stgit@pluto.themaw.net> References: <20161003003646.4865.42500.stgit@pluto.themaw.net> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d=themaw.net; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-sasl-enc :x-sasl-enc; s=mesmtp; bh=JusLi/FNzTuGh46VAIVtijPnChc=; b=S7Utpt 0WF00ZDNmoayd68Ys+xGkutNzhGQpPl2+tnF6eUw+qCr6uI0NEdt8XLiJQ24Fra+ 0TWcujdJf+kU/WpaSZxYhx9zZHqGSDWwRuKXB+sTgaUJUeEMQWEU5ak74CRXgl2g MJf4hElgnd1930VyyYU3TqDuQLZP+lKiOPse0= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:in-reply-to:message-id:mime-version:references :subject:to:x-sasl-enc:x-sasl-enc; s=smtpout; bh=JusLi/FNzTuGh46 VAIVtijPnChc=; b=cv6mXlwC39nhtFD8OP+nj0h/zVtXnQdKwHRohRWMVkUihsd Wp/LaVpuCqNAm+u9NIoFxESvFUnECN4NkkcL0z6uNYXXob8uD7tDtlucfbReACRq Gs7rqJs/2PsXDx//kaZAtwcWzeaADDZJ0dIDje2OPwvk26ddtnG57yj+Vp5A= In-Reply-To: <20161003003646.4865.42500.stgit@pluto.themaw.net> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Kernel Mailing List Cc: autofs mailing list , Al Viro , linux-fsdevel , Omar Sandoval , Andrew Morton , "Eric W. Biederman" From: Ian Kent If an automount mount is clone(2)ed into a file system that is propagation private, when it later expires in the originating namespace, subsequent calls to autofs ->d_automount() for that dentry in the original namespace will return ELOOP until the mount is umounted in the cloned namespace. Now that a struct path is available where needed use path_is_mountpoint() instead of d_mountpoint() so we don't get false positives when checking if a dentry is a mount point in the current namespace. Signed-off-by: Ian Kent Cc: Al Viro Cc: Eric W. Biederman Cc: Omar Sandoval --- fs/autofs4/root.c | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-) diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c index a12c248..0f5d264 100644 --- a/fs/autofs4/root.c +++ b/fs/autofs4/root.c @@ -107,12 +107,15 @@ static int autofs4_dir_open(struct inode *inode, struct file *file) { struct dentry *dentry = file->f_path.dentry; struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb); + struct path path; pr_debug("file=%p dentry=%p %pd\n", file, dentry, dentry); if (autofs4_oz_mode(sbi)) goto out; + path = file->f_path; + /* * An empty directory in an autofs file system is always a * mount point. The daemon must have failed to mount this @@ -123,7 +126,7 @@ static int autofs4_dir_open(struct inode *inode, struct file *file) * it. */ spin_lock(&sbi->lookup_lock); - if (!d_mountpoint(dentry) && simple_empty(dentry)) { + if (!path_is_mountpoint(&path) && simple_empty(dentry)) { spin_unlock(&sbi->lookup_lock); return -ENOENT; } @@ -372,15 +375,15 @@ static struct vfsmount *autofs4_d_automount(struct path *path) /* * If the dentry is a symlink it's equivalent to a directory - * having d_mountpoint() true, so there's no need to call back - * to the daemon. + * having path_is_mountpoint() true, so there's no need to call + * back to the daemon. */ if (d_really_is_positive(dentry) && d_is_symlink(dentry)) { spin_unlock(&sbi->fs_lock); goto done; } - if (!d_mountpoint(dentry)) { + if (!path_is_mountpoint(path)) { /* * It's possible that user space hasn't removed directories * after umounting a rootless multi-mount, although it @@ -434,8 +437,13 @@ static int autofs4_d_manage(struct path *path, bool rcu_walk) /* The daemon never waits. */ if (autofs4_oz_mode(sbi)) { - if (!d_mountpoint(dentry)) - return -EISDIR; + if (rcu_walk) { + if (!path_is_mountpoint_rcu(path)) + return -EISDIR; + } else { + if (!path_is_mountpoint(path)) + return -EISDIR; + } return 0; } @@ -463,7 +471,7 @@ static int autofs4_d_manage(struct path *path, bool rcu_walk) if (ino->flags & AUTOFS_INF_WANT_EXPIRE) return 0; - if (d_mountpoint(dentry)) + if (path_is_mountpoint_rcu(path)) return 0; inode = d_inode_rcu(dentry); if (inode && S_ISLNK(inode->i_mode)) @@ -490,7 +498,7 @@ static int autofs4_d_manage(struct path *path, bool rcu_walk) * we can avoid needless calls ->d_automount() and avoid * an incorrect ELOOP error return. */ - if ((!d_mountpoint(dentry) && !simple_empty(dentry)) || + if ((!path_is_mountpoint(path) && !simple_empty(dentry)) || (d_really_is_positive(dentry) && d_is_symlink(dentry))) status = -EISDIR; }