1 files changed, 126 insertions, 8 deletions

diff --git a/fs/open.c b/fs/open.c
index 5a2c6ebc22b..3cac0bda46d 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -233,6 +233,14 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 
 	if (!(file->f_mode & FMODE_WRITE))
 		return -EBADF;
+
+	/* It's not possible punch hole on append only file */
+	if (mode & FALLOC_FL_PUNCH_HOLE && IS_APPEND(inode))
+		return -EPERM;
+
+	if (IS_IMMUTABLE(inode))
+		return -EPERM;
+
 	/*
 	 * Revalidate the write permissions, in case security policy has
 	 * changed since the files were opened.
@@ -565,13 +573,15 @@ SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
 {
 	struct path path;
 	int error = -EINVAL;
-	int follow;
+	int lookup_flags;
 
-	if ((flag & ~AT_SYMLINK_NOFOLLOW) != 0)
+	if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 		goto out;
 
-	follow = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
-	error = user_path_at(dfd, filename, follow, &path);
+	lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
+	if (flag & AT_EMPTY_PATH)
+		lookup_flags |= LOOKUP_EMPTY;
+	error = user_path_at(dfd, filename, lookup_flags, &path);
 	if (error)
 		goto out;
 	error = mnt_want_write(path.mnt);
@@ -661,11 +671,16 @@ static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
 					int (*open)(struct inode *, struct file *),
 					const struct cred *cred)
 {
+	static const struct file_operations empty_fops = {};
 	struct inode *inode;
 	int error;
 
 	f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
 				FMODE_PREAD | FMODE_PWRITE;
+
+	if (unlikely(f->f_flags & O_PATH))
+		f->f_mode = FMODE_PATH;
+
 	inode = dentry->d_inode;
 	if (f->f_mode & FMODE_WRITE) {
 		error = __get_file_write_access(inode, mnt);
@@ -679,9 +694,15 @@ static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
 	f->f_path.dentry = dentry;
 	f->f_path.mnt = mnt;
 	f->f_pos = 0;
-	f->f_op = fops_get(inode->i_fop);
 	file_sb_list_add(f, inode->i_sb);
 
+	if (unlikely(f->f_mode & FMODE_PATH)) {
+		f->f_op = &empty_fops;
+		return f;
+	}
+
+	f->f_op = fops_get(inode->i_fop);
+
 	error = security_dentry_open(f, cred);
 	if (error)
 		goto cleanup_all;
@@ -882,15 +903,110 @@ void fd_install(unsigned int fd, struct file *file)
 
 EXPORT_SYMBOL(fd_install);
 
+static inline int build_open_flags(int flags, int mode, struct open_flags *op)
+{
+	int lookup_flags = 0;
+	int acc_mode;
+
+	if (!(flags & O_CREAT))
+		mode = 0;
+	op->mode = mode;
+
+	/* Must never be set by userspace */
+	flags &= ~FMODE_NONOTIFY;
+
+	/*
+	 * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
+	 * check for O_DSYNC if the need any syncing at all we enforce it's
+	 * always set instead of having to deal with possibly weird behaviour
+	 * for malicious applications setting only __O_SYNC.
+	 */
+	if (flags & __O_SYNC)
+		flags |= O_DSYNC;
+
+	/*
+	 * If we have O_PATH in the open flag. Then we
+	 * cannot have anything other than the below set of flags
+	 */
+	if (flags & O_PATH) {
+		flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
+		acc_mode = 0;
+	} else {
+		acc_mode = MAY_OPEN | ACC_MODE(flags);
+	}
+
+	op->open_flag = flags;
+
+	/* O_TRUNC implies we need access checks for write permissions */
+	if (flags & O_TRUNC)
+		acc_mode |= MAY_WRITE;
+
+	/* Allow the LSM permission hook to distinguish append
+	   access from general write access. */
+	if (flags & O_APPEND)
+		acc_mode |= MAY_APPEND;
+
+	op->acc_mode = acc_mode;
+
+	op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
+
+	if (flags & O_CREAT) {
+		op->intent |= LOOKUP_CREATE;
+		if (flags & O_EXCL)
+			op->intent |= LOOKUP_EXCL;
+	}
+
+	if (flags & O_DIRECTORY)
+		lookup_flags |= LOOKUP_DIRECTORY;
+	if (!(flags & O_NOFOLLOW))
+		lookup_flags |= LOOKUP_FOLLOW;
+	return lookup_flags;
+}
+
+/**
+ * filp_open - open file and return file pointer
+ *
+ * @filename:	path to open
+ * @flags:	open flags as per the open(2) second argument
+ * @mode:	mode for the new file if O_CREAT is set, else ignored
+ *
+ * This is the helper to open a file from kernelspace if you really
+ * have to.  But in generally you should not do this, so please move
+ * along, nothing to see here..
+ */
+struct file *filp_open(const char *filename, int flags, int mode)
+{
+	struct open_flags op;
+	int lookup = build_open_flags(flags, mode, &op);
+	return do_filp_open(AT_FDCWD, filename, &op, lookup);
+}
+EXPORT_SYMBOL(filp_open);
+
+struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
+			    const char *filename, int flags)
+{
+	struct open_flags op;
+	int lookup = build_open_flags(flags, 0, &op);
+	if (flags & O_CREAT)
+		return ERR_PTR(-EINVAL);
+	if (!filename && (flags & O_DIRECTORY))
+		if (!dentry->d_inode->i_op->lookup)
+			return ERR_PTR(-ENOTDIR);
+	return do_file_open_root(dentry, mnt, filename, &op, lookup);
+}
+EXPORT_SYMBOL(file_open_root);
+
 long do_sys_open(int dfd, const char __user *filename, int flags, int mode)
 {
+	struct open_flags op;
+	int lookup = build_open_flags(flags, mode, &op);
 	char *tmp = getname(filename);
 	int fd = PTR_ERR(tmp);
 
 	if (!IS_ERR(tmp)) {
 		fd = get_unused_fd_flags(flags);
 		if (fd >= 0) {
-			struct file *f = do_filp_open(dfd, tmp, flags, mode, 0);
+			struct file *f = do_filp_open(dfd, tmp, &op, lookup);
 			if (IS_ERR(f)) {
 				put_unused_fd(fd);
 				fd = PTR_ERR(f);
@@ -960,8 +1076,10 @@ int filp_close(struct file *filp, fl_owner_t id)
 	if (filp->f_op && filp->f_op->flush)
 		retval = filp->f_op->flush(filp, id);
 
-	dnotify_flush(filp, id);
-	locks_remove_posix(filp, id);
+	if (likely(!(filp->f_mode & FMODE_PATH))) {
+		dnotify_flush(filp, id);
+		locks_remove_posix(filp, id);
+	}
 	fput(filp);
 	return retval;
 }