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: