Merge branch 'work.mqueue' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull mqueue/bpf vfs cleanups from Al Viro:
 "mqueue and bpf go through rather painful and similar contortions to
  create objects in their dentry trees. Provide a primitive for doing
  that without abusing ->mknod(), switch bpf and mqueue to it.

  Another mqueue-related thing that has ended up in that branch is
  on-demand creation of internal mount (based upon the work of Giuseppe
  Scrivano)"

* 'work.mqueue' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  mqueue: switch to on-demand creation of internal mount
  tidy do_mq_open() up a bit
  mqueue: clean prepare_open() up
  do_mq_open(): move all work prior to dentry_open() into a helper
  mqueue: fold mq_attr_ok() into mqueue_get_inode()
  move dentry_open() calls up into do_mq_open()
  mqueue: switch to vfs_mkobj(), quit abusing ->d_fsdata
  bpf_obj_do_pin(): switch to vfs_mkobj(), quit abusing ->mknod()
  new primitive: vfs_mkobj()

1 files changed, 111 insertions, 130 deletions

diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 3bc5bb7d6827..690ae6665500 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -270,13 +270,30 @@ static struct inode *mqueue_get_inode(struct super_block *sb,
 		 * that means the min(mq_maxmsg, max_priorities) * struct
 		 * posix_msg_tree_node.
 		 */
+
+		ret = -EINVAL;
+		if (info->attr.mq_maxmsg <= 0 || info->attr.mq_msgsize <= 0)
+			goto out_inode;
+		if (capable(CAP_SYS_RESOURCE)) {
+			if (info->attr.mq_maxmsg > HARD_MSGMAX ||
+			    info->attr.mq_msgsize > HARD_MSGSIZEMAX)
+				goto out_inode;
+		} else {
+			if (info->attr.mq_maxmsg > ipc_ns->mq_msg_max ||
+					info->attr.mq_msgsize > ipc_ns->mq_msgsize_max)
+				goto out_inode;
+		}
+		ret = -EOVERFLOW;
+		/* check for overflow */
+		if (info->attr.mq_msgsize > ULONG_MAX/info->attr.mq_maxmsg)
+			goto out_inode;
 		mq_treesize = info->attr.mq_maxmsg * sizeof(struct msg_msg) +
 			min_t(unsigned int, info->attr.mq_maxmsg, MQ_PRIO_MAX) *
 			sizeof(struct posix_msg_tree_node);
-
-		mq_bytes = mq_treesize + (info->attr.mq_maxmsg *
-					  info->attr.mq_msgsize);
-
+		mq_bytes = info->attr.mq_maxmsg * info->attr.mq_msgsize;
+		if (mq_bytes + mq_treesize < mq_bytes)
+			goto out_inode;
+		mq_bytes += mq_treesize;
 		spin_lock(&mq_lock);
 		if (u->mq_bytes + mq_bytes < u->mq_bytes ||
 		    u->mq_bytes + mq_bytes > rlimit(RLIMIT_MSGQUEUE)) {
@@ -308,8 +325,9 @@ err:
 static int mqueue_fill_super(struct super_block *sb, void *data, int silent)
 {
 	struct inode *inode;
-	struct ipc_namespace *ns = sb->s_fs_info;
+	struct ipc_namespace *ns = data;
 
+	sb->s_fs_info = ns;
 	sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
 	sb->s_blocksize = PAGE_SIZE;
 	sb->s_blocksize_bits = PAGE_SHIFT;
@@ -326,18 +344,44 @@ static int mqueue_fill_super(struct super_block *sb, void *data, int silent)
 	return 0;
 }
 
+static struct file_system_type mqueue_fs_type;
+/*
+ * Return value is pinned only by reference in ->mq_mnt; it will
+ * live until ipcns dies.  Caller does not need to drop it.
+ */
+static struct vfsmount *mq_internal_mount(void)
+{
+	struct ipc_namespace *ns = current->nsproxy->ipc_ns;
+	struct vfsmount *m = ns->mq_mnt;
+	if (m)
+		return m;
+	m = kern_mount_data(&mqueue_fs_type, ns);
+	spin_lock(&mq_lock);
+	if (unlikely(ns->mq_mnt)) {
+		spin_unlock(&mq_lock);
+		if (!IS_ERR(m))
+			kern_unmount(m);
+		return ns->mq_mnt;
+	}
+	if (!IS_ERR(m))
+		ns->mq_mnt = m;
+	spin_unlock(&mq_lock);
+	return m;
+}
+
 static struct dentry *mqueue_mount(struct file_system_type *fs_type,
 			 int flags, const char *dev_name,
 			 void *data)
 {
-	struct ipc_namespace *ns;
-	if (flags & SB_KERNMOUNT) {
-		ns = data;
-		data = NULL;
-	} else {
-		ns = current->nsproxy->ipc_ns;
-	}
-	return mount_ns(fs_type, flags, data, ns, ns->user_ns, mqueue_fill_super);
+	struct vfsmount *m;
+	if (flags & SB_KERNMOUNT)
+		return mount_nodev(fs_type, flags, data, mqueue_fill_super);
+	m = mq_internal_mount();
+	if (IS_ERR(m))
+		return ERR_CAST(m);
+	atomic_inc(&m->mnt_sb->s_active);
+	down_write(&m->mnt_sb->s_umount);
+	return dget(m->mnt_root);
 }
 
 static void init_once(void *foo)
@@ -416,11 +460,11 @@ static void mqueue_evict_inode(struct inode *inode)
 		put_ipc_ns(ipc_ns);
 }
 
-static int mqueue_create(struct inode *dir, struct dentry *dentry,
-				umode_t mode, bool excl)
+static int mqueue_create_attr(struct dentry *dentry, umode_t mode, void *arg)
 {
+	struct inode *dir = dentry->d_parent->d_inode;
 	struct inode *inode;
-	struct mq_attr *attr = dentry->d_fsdata;
+	struct mq_attr *attr = arg;
 	int error;
 	struct ipc_namespace *ipc_ns;
 
@@ -461,6 +505,12 @@ out_unlock:
 	return error;
 }
 
+static int mqueue_create(struct inode *dir, struct dentry *dentry,
+				umode_t mode, bool excl)
+{
+	return mqueue_create_attr(dentry, mode, NULL);
+}
+
 static int mqueue_unlink(struct inode *dir, struct dentry *dentry)
 {
 	struct inode *inode = d_inode(dentry);
@@ -691,96 +741,46 @@ static void remove_notification(struct mqueue_inode_info *info)
 	info->notify_user_ns = NULL;
 }
 
-static int mq_attr_ok(struct ipc_namespace *ipc_ns, struct mq_attr *attr)
-{
-	int mq_treesize;
-	unsigned long total_size;
-
-	if (attr->mq_maxmsg <= 0 || attr->mq_msgsize <= 0)
-		return -EINVAL;
-	if (capable(CAP_SYS_RESOURCE)) {
-		if (attr->mq_maxmsg > HARD_MSGMAX ||
-		    attr->mq_msgsize > HARD_MSGSIZEMAX)
-			return -EINVAL;
-	} else {
-		if (attr->mq_maxmsg > ipc_ns->mq_msg_max ||
-				attr->mq_msgsize > ipc_ns->mq_msgsize_max)
-			return -EINVAL;
-	}
-	/* check for overflow */
-	if (attr->mq_msgsize > ULONG_MAX/attr->mq_maxmsg)
-		return -EOVERFLOW;
-	mq_treesize = attr->mq_maxmsg * sizeof(struct msg_msg) +
-		min_t(unsigned int, attr->mq_maxmsg, MQ_PRIO_MAX) *
-		sizeof(struct posix_msg_tree_node);
-	total_size = attr->mq_maxmsg * attr->mq_msgsize;
-	if (total_size + mq_treesize < total_size)
-		return -EOVERFLOW;
-	return 0;
-}
-
-/*
- * Invoked when creating a new queue via sys_mq_open
- */
-static struct file *do_create(struct ipc_namespace *ipc_ns, struct inode *dir,
-			struct path *path, int oflag, umode_t mode,
+static int prepare_open(struct dentry *dentry, int oflag, int ro,
+			umode_t mode, struct filename *name,
 			struct mq_attr *attr)
 {
-	const struct cred *cred = current_cred();
-	int ret;
-
-	if (attr) {
-		ret = mq_attr_ok(ipc_ns, attr);
-		if (ret)
-			return ERR_PTR(ret);
-		/* store for use during create */
-		path->dentry->d_fsdata = attr;
-	} else {
-		struct mq_attr def_attr;
-
-		def_attr.mq_maxmsg = min(ipc_ns->mq_msg_max,
-					 ipc_ns->mq_msg_default);
-		def_attr.mq_msgsize = min(ipc_ns->mq_msgsize_max,
-					  ipc_ns->mq_msgsize_default);
-		ret = mq_attr_ok(ipc_ns, &def_attr);
-		if (ret)
-			return ERR_PTR(ret);
-	}
-
-	mode &= ~current_umask();
-	ret = vfs_create(dir, path->dentry, mode, true);
-	path->dentry->d_fsdata = NULL;
-	if (ret)
-		return ERR_PTR(ret);
-	return dentry_open(path, oflag, cred);
-}
-
-/* Opens existing queue */
-static struct file *do_open(struct path *path, int oflag)
-{
 	static const int oflag2acc[O_ACCMODE] = { MAY_READ, MAY_WRITE,
 						  MAY_READ | MAY_WRITE };
 	int acc;
+
+	if (d_really_is_negative(dentry)) {
+		if (!(oflag & O_CREAT))
+			return -ENOENT;
+		if (ro)
+			return ro;
+		audit_inode_parent_hidden(name, dentry->d_parent);
+		return vfs_mkobj(dentry, mode & ~current_umask(),
+				  mqueue_create_attr, attr);
+	}
+	/* it already existed */
+	audit_inode(name, dentry, 0);
+	if ((oflag & (O_CREAT|O_EXCL)) == (O_CREAT|O_EXCL))
+		return -EEXIST;
 	if ((oflag & O_ACCMODE) == (O_RDWR | O_WRONLY))
-		return ERR_PTR(-EINVAL);
+		return -EINVAL;
 	acc = oflag2acc[oflag & O_ACCMODE];
-	if (inode_permission(d_inode(path->dentry), acc))
-		return ERR_PTR(-EACCES);
-	return dentry_open(path, oflag, current_cred());
+	return inode_permission(d_inode(dentry), acc);
 }
 
 static int do_mq_open(const char __user *u_name, int oflag, umode_t mode,
 		      struct mq_attr *attr)
 {
-	struct path path;
-	struct file *filp;
+	struct vfsmount *mnt = mq_internal_mount();
+	struct dentry *root;
 	struct filename *name;
+	struct path path;
 	int fd, error;
-	struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
-	struct vfsmount *mnt = ipc_ns->mq_mnt;
-	struct dentry *root = mnt->mnt_root;
 	int ro;
 
+	if (IS_ERR(mnt))
+		return PTR_ERR(mnt);
+
 	audit_mq_open(oflag, mode, attr);
 
 	if (IS_ERR(name = getname(u_name)))
@@ -791,7 +791,7 @@ static int do_mq_open(const char __user *u_name, int oflag, umode_t mode,
 		goto out_putname;
 
 	ro = mnt_want_write(mnt);	/* we'll drop it in any case */
-	error = 0;
+	root = mnt->mnt_root;
 	inode_lock(d_inode(root));
 	path.dentry = lookup_one_len(name->name, root, strlen(name->name));
 	if (IS_ERR(path.dentry)) {
@@ -799,38 +799,14 @@ static int do_mq_open(const char __user *u_name, int oflag, umode_t mode,
 		goto out_putfd;
 	}
 	path.mnt = mntget(mnt);
-
-	if (oflag & O_CREAT) {
-		if (d_really_is_positive(path.dentry)) {	/* entry already exists */
-			audit_inode(name, path.dentry, 0);
-			if (oflag & O_EXCL) {
-				error = -EEXIST;
-				goto out;
-			}
-			filp = do_open(&path, oflag);
-		} else {
-			if (ro) {
-				error = ro;
-				goto out;
-			}
-			audit_inode_parent_hidden(name, root);
-			filp = do_create(ipc_ns, d_inode(root), &path,
-					 oflag, mode, attr);
-		}
-	} else {
-		if (d_really_is_negative(path.dentry)) {
-			error = -ENOENT;
-			goto out;
-		}
-		audit_inode(name, path.dentry, 0);
-		filp = do_open(&path, oflag);
+	error = prepare_open(path.dentry, oflag, ro, mode, name, attr);
+	if (!error) {
+		struct file *file = dentry_open(&path, oflag, current_cred());
+		if (!IS_ERR(file))
+			fd_install(fd, file);
+		else
+			error = PTR_ERR(file);
 	}
-
-	if (!IS_ERR(filp))
-		fd_install(fd, filp);
-	else
-		error = PTR_ERR(filp);
-out:
 	path_put(&path);
 out_putfd:
 	if (error) {
@@ -864,6 +840,9 @@ SYSCALL_DEFINE1(mq_unlink, const char __user *, u_name)
 	struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
 	struct vfsmount *mnt = ipc_ns->mq_mnt;
 
+	if (!mnt)
+		return -ENOENT;
+
 	name = getname(u_name);
 	if (IS_ERR(name))
 		return PTR_ERR(name);
@@ -1590,28 +1569,26 @@ int mq_init_ns(struct ipc_namespace *ns)
 	ns->mq_msgsize_max   = DFLT_MSGSIZEMAX;
 	ns->mq_msg_default   = DFLT_MSG;
 	ns->mq_msgsize_default  = DFLT_MSGSIZE;
+	ns->mq_mnt = NULL;
 
-	ns->mq_mnt = kern_mount_data(&mqueue_fs_type, ns);
-	if (IS_ERR(ns->mq_mnt)) {
-		int err = PTR_ERR(ns->mq_mnt);
-		ns->mq_mnt = NULL;
-		return err;
-	}
 	return 0;
 }
 
 void mq_clear_sbinfo(struct ipc_namespace *ns)
 {
-	ns->mq_mnt->mnt_sb->s_fs_info = NULL;
+	if (ns->mq_mnt)
+		ns->mq_mnt->mnt_sb->s_fs_info = NULL;
 }
 
 void mq_put_mnt(struct ipc_namespace *ns)
 {
-	kern_unmount(ns->mq_mnt);
+	if (ns->mq_mnt)
+		kern_unmount(ns->mq_mnt);
 }
 
 static int __init init_mqueue_fs(void)
 {
+	struct vfsmount *m;
 	int error;
 
 	mqueue_inode_cachep = kmem_cache_create("mqueue_inode_cache",
@@ -1633,6 +1610,10 @@ static int __init init_mqueue_fs(void)
 	if (error)
 		goto out_filesystem;
 
+	m = kern_mount_data(&mqueue_fs_type, &init_ipc_ns);
+	if (IS_ERR(m))
+		goto out_filesystem;
+	init_ipc_ns.mq_mnt = m;
 	return 0;
 
 out_filesystem: