1 files changed, 112 insertions, 60 deletions

diff --git a/fs/stat.c b/fs/stat.c
index 70bd3e888cfa..6f65b3456cad 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -214,6 +214,43 @@ int getname_statx_lookup_flags(int flags)
 	return lookup_flags;
 }
 
+static int vfs_statx_path(struct path *path, int flags, struct kstat *stat,
+			  u32 request_mask)
+{
+	int error = vfs_getattr(path, stat, request_mask, flags);
+
+	if (request_mask & STATX_MNT_ID_UNIQUE) {
+		stat->mnt_id = real_mount(path->mnt)->mnt_id_unique;
+		stat->result_mask |= STATX_MNT_ID_UNIQUE;
+	} else {
+		stat->mnt_id = real_mount(path->mnt)->mnt_id;
+		stat->result_mask |= STATX_MNT_ID;
+	}
+
+	if (path_mounted(path))
+		stat->attributes |= STATX_ATTR_MOUNT_ROOT;
+	stat->attributes_mask |= STATX_ATTR_MOUNT_ROOT;
+
+	/* Handle STATX_DIOALIGN for block devices. */
+	if (request_mask & STATX_DIOALIGN) {
+		struct inode *inode = d_backing_inode(path->dentry);
+
+		if (S_ISBLK(inode->i_mode))
+			bdev_statx_dioalign(inode, stat);
+	}
+
+	return error;
+}
+
+static int vfs_statx_fd(int fd, int flags, struct kstat *stat,
+			  u32 request_mask)
+{
+	CLASS(fd_raw, f)(fd);
+	if (!f.file)
+		return -EBADF;
+	return vfs_statx_path(&f.file->f_path, flags, stat, request_mask);
+}
+
 /**
  * vfs_statx - Get basic and extra attributes by filename
  * @dfd: A file descriptor representing the base dir for a relative filename
@@ -243,36 +280,13 @@ static int vfs_statx(int dfd, struct filename *filename, int flags,
 retry:
 	error = filename_lookup(dfd, filename, lookup_flags, &path, NULL);
 	if (error)
-		goto out;
-
-	error = vfs_getattr(&path, stat, request_mask, flags);
-
-	if (request_mask & STATX_MNT_ID_UNIQUE) {
-		stat->mnt_id = real_mount(path.mnt)->mnt_id_unique;
-		stat->result_mask |= STATX_MNT_ID_UNIQUE;
-	} else {
-		stat->mnt_id = real_mount(path.mnt)->mnt_id;
-		stat->result_mask |= STATX_MNT_ID;
-	}
-
-	if (path.mnt->mnt_root == path.dentry)
-		stat->attributes |= STATX_ATTR_MOUNT_ROOT;
-	stat->attributes_mask |= STATX_ATTR_MOUNT_ROOT;
-
-	/* Handle STATX_DIOALIGN for block devices. */
-	if (request_mask & STATX_DIOALIGN) {
-		struct inode *inode = d_backing_inode(path.dentry);
-
-		if (S_ISBLK(inode->i_mode))
-			bdev_statx_dioalign(inode, stat);
-	}
-
+		return error;
+	error = vfs_statx_path(&path, flags, stat, request_mask);
 	path_put(&path);
 	if (retry_estale(error, lookup_flags)) {
 		lookup_flags |= LOOKUP_REVAL;
 		goto retry;
 	}
-out:
 	return error;
 }
 
@@ -289,18 +303,10 @@ int vfs_fstatat(int dfd, const char __user *filename,
 	 * If AT_EMPTY_PATH is set, we expect the common case to be that
 	 * empty path, and avoid doing all the extra pathname work.
 	 */
-	if (dfd >= 0 && flags == AT_EMPTY_PATH) {
-		char c;
-
-		ret = get_user(c, filename);
-		if (unlikely(ret))
-			return ret;
-
-		if (likely(!c))
-			return vfs_fstat(dfd, stat);
-	}
+	if (flags == AT_EMPTY_PATH && vfs_empty_path(dfd, filename))
+		return vfs_fstat(dfd, stat);
 
-	name = getname_flags(filename, getname_statx_lookup_flags(statx_flags), NULL);
+	name = getname_flags(filename, getname_statx_lookup_flags(statx_flags));
 	ret = vfs_statx(dfd, name, statx_flags, stat, STATX_BASIC_STATS);
 	putname(name);
 
@@ -488,34 +494,39 @@ static int do_readlinkat(int dfd, const char __user *pathname,
 			 char __user *buf, int bufsiz)
 {
 	struct path path;
+	struct filename *name;
 	int error;
-	int empty = 0;
 	unsigned int lookup_flags = LOOKUP_EMPTY;
 
 	if (bufsiz <= 0)
 		return -EINVAL;
 
 retry:
-	error = user_path_at_empty(dfd, pathname, lookup_flags, &path, &empty);
-	if (!error) {
-		struct inode *inode = d_backing_inode(path.dentry);
-
-		error = empty ? -ENOENT : -EINVAL;
-		/*
-		 * AFS mountpoints allow readlink(2) but are not symlinks
-		 */
-		if (d_is_symlink(path.dentry) || inode->i_op->readlink) {
-			error = security_inode_readlink(path.dentry);
-			if (!error) {
-				touch_atime(&path);
-				error = vfs_readlink(path.dentry, buf, bufsiz);
-			}
-		}
-		path_put(&path);
-		if (retry_estale(error, lookup_flags)) {
-			lookup_flags |= LOOKUP_REVAL;
-			goto retry;
+	name = getname_flags(pathname, lookup_flags);
+	error = filename_lookup(dfd, name, lookup_flags, &path, NULL);
+	if (unlikely(error)) {
+		putname(name);
+		return error;
+	}
+
+	/*
+	 * AFS mountpoints allow readlink(2) but are not symlinks
+	 */
+	if (d_is_symlink(path.dentry) ||
+	    d_backing_inode(path.dentry)->i_op->readlink) {
+		error = security_inode_readlink(path.dentry);
+		if (!error) {
+			touch_atime(&path);
+			error = vfs_readlink(path.dentry, buf, bufsiz);
 		}
+	} else {
+		error = (name->name[0] == '\0') ? -ENOENT : -EINVAL;
+	}
+	path_put(&path);
+	putname(name);
+	if (retry_estale(error, lookup_flags)) {
+		lookup_flags |= LOOKUP_REVAL;
+		goto retry;
 	}
 	return error;
 }
@@ -674,7 +685,8 @@ int do_statx(int dfd, struct filename *filename, unsigned int flags,
 	if ((flags & AT_STATX_SYNC_TYPE) == AT_STATX_SYNC_TYPE)
 		return -EINVAL;
 
-	/* STATX_CHANGE_COOKIE is kernel-only for now. Ignore requests
+	/*
+	 * STATX_CHANGE_COOKIE is kernel-only for now. Ignore requests
 	 * from userland.
 	 */
 	mask &= ~STATX_CHANGE_COOKIE;
@@ -686,16 +698,41 @@ int do_statx(int dfd, struct filename *filename, unsigned int flags,
 	return cp_statx(&stat, buffer);
 }
 
+int do_statx_fd(int fd, unsigned int flags, unsigned int mask,
+	     struct statx __user *buffer)
+{
+	struct kstat stat;
+	int error;
+
+	if (mask & STATX__RESERVED)
+		return -EINVAL;
+	if ((flags & AT_STATX_SYNC_TYPE) == AT_STATX_SYNC_TYPE)
+		return -EINVAL;
+
+	/*
+	 * STATX_CHANGE_COOKIE is kernel-only for now. Ignore requests
+	 * from userland.
+	 */
+	mask &= ~STATX_CHANGE_COOKIE;
+
+	error = vfs_statx_fd(fd, flags, &stat, mask);
+	if (error)
+		return error;
+
+	return cp_statx(&stat, buffer);
+}
+
 /**
  * sys_statx - System call to get enhanced stats
  * @dfd: Base directory to pathwalk from *or* fd to stat.
- * @filename: File to stat or "" with AT_EMPTY_PATH
+ * @filename: File to stat or either NULL or "" with AT_EMPTY_PATH
  * @flags: AT_* flags to control pathwalk.
  * @mask: Parts of statx struct actually required.
  * @buffer: Result buffer.
  *
  * Note that fstat() can be emulated by setting dfd to the fd of interest,
- * supplying "" as the filename and setting AT_EMPTY_PATH in the flags.
+ * supplying "" (or preferably NULL) as the filename and setting AT_EMPTY_PATH
+ * in the flags.
  */
 SYSCALL_DEFINE5(statx,
 		int, dfd, const char __user *, filename, unsigned, flags,
@@ -703,9 +740,24 @@ SYSCALL_DEFINE5(statx,
 		struct statx __user *, buffer)
 {
 	int ret;
+	unsigned lflags;
 	struct filename *name;
 
-	name = getname_flags(filename, getname_statx_lookup_flags(flags), NULL);
+	/*
+	 * Short-circuit handling of NULL and "" paths.
+	 *
+	 * For a NULL path we require and accept only the AT_EMPTY_PATH flag
+	 * (possibly |'d with AT_STATX flags).
+	 *
+	 * However, glibc on 32-bit architectures implements fstatat as statx
+	 * with the "" pathname and AT_NO_AUTOMOUNT | AT_EMPTY_PATH flags.
+	 * Supporting this results in the uglification below.
+	 */
+	lflags = flags & ~(AT_NO_AUTOMOUNT | AT_STATX_SYNC_TYPE);
+	if (lflags == AT_EMPTY_PATH && vfs_empty_path(dfd, filename))
+		return do_statx_fd(dfd, flags & ~AT_NO_AUTOMOUNT, mask, buffer);
+
+	name = getname_flags(filename, getname_statx_lookup_flags(flags));
 	ret = do_statx(dfd, name, flags, mask, buffer);
 	putname(name);