Fix mount permission issue

Signed-off-by: Umer Saleem <[email protected]>

contrib/initramfs/scripts/zfs

@@ -345,7 +345,7 @@ mount_fs()
 
 	# Need the _original_ datasets mountpoint!
 	mountpoint=$(get_fs_value "$fs" mountpoint)
-	ZFS_CMD="mount -o zfsutil -t zfs"
+	ZFS_CMD="mount.zfs -o zfsutil"
 	if [ "$mountpoint" = "legacy" ] || [ "$mountpoint" = "none" ]; then
 		# Can't use the mountpoint property. Might be one of our
 		# clones. Check the 'org.zol:mountpoint' property set in
@@ -362,7 +362,7 @@ mount_fs()
 			fi
 			# Don't use mount.zfs -o zfsutils for legacy mountpoint
 			if [ "$mountpoint" = "legacy" ]; then
-				ZFS_CMD="mount -t zfs"
+				ZFS_CMD="mount.zfs"
 			fi
 			# Last hail-mary: Hope 'rootmnt' is set!
 			mountpoint=""

module/os/linux/zfs/zfs_ctldir.c

@@ -1049,6 +1049,68 @@ exportfs_flush(void)
 	(void) call_usermodehelper(argv[0], argv, envp, UMH_WAIT_PROC);
 }
 
+/*
+ * Returns the path in char format for given struct path. Uses
+ * d_path exported by kernel to convert struct path to char
+ * format. Returns the correct path for mountpoints and chroot
+ * environments.
+ *
+ * If chroot environment has directories that are mounted with
+ * --bind or --rbind flag, d_path returns the complete path inside
+ * chroot environment but does not return the absolute path, i.e.
+ * the path to chroot environment is missing.
+ */
+static int
+get_root_path(struct path *path, char *buff, int len)
+{
+	char *path_buffer, *path_ptr;
+	int path_len, error = 0;
+
+	path_get(path);
+	path_buffer = kmem_zalloc(len, KM_SLEEP);
+	path_ptr = d_path(path, path_buffer, len);
+	if (IS_ERR(path_ptr)) {
+		error = SET_ERROR(-PTR_ERR(path_ptr));
+		goto out;
+	}
+	path_len = path_buffer + len - 1 - path_ptr;
+	if (path_len > len) {
+		error = SET_ERROR(EFAULT);
+		goto out;
+	}
+	memcpy(buff, path_ptr, path_len);
+	buff[path_len] = '\0';
+
+out:
+	kmem_free(path_buffer, len);
+	path_put(path);
+	return (error);
+}
+
+/*
+ * Returns if the current process root is chrooted or not.
+ */
+static int
+is_current_chrooted(void)
+{
+	struct task_struct *curr = current, *global = &init_task;
+	struct path gl_root;
+	struct path cr_root;
+	int chrooted;
+
+	get_fs_root(global->fs, &gl_root);
+	while (d_mountpoint(gl_root.dentry) && follow_down_one(&gl_root))
+		;
+
+	get_fs_root(curr->fs, &cr_root);
+	chrooted = !path_equal(&cr_root, &gl_root);
+
+	path_put(&cr_root);
+	path_put(&gl_root);
+
+	return (chrooted);
+}
+
 /*
  * Attempt to unmount a snapshot by making a call to user space.
  * There is no assurance that this can or will succeed, is just a
@@ -1122,6 +1184,37 @@ zfsctl_snapshot_mount(struct path *path, int flags)
 	if (error)
 		goto error;
 
+	if (is_current_chrooted() == 0) {
+		/*
+		 * Current process is not in chroot context
+		 */
+		if (zfsvfs->z_vfs->vfs_mntpoint != NULL) {
+			char *m = kmem_zalloc(MAXPATHLEN, KM_SLEEP);
+			struct path mnt_path;
+			mnt_path.mnt = path->mnt;
+			mnt_path.dentry = path->mnt->mnt_root;
+
+			/*
+			 * Get path to current mountpoint
+			 */
+			error = get_root_path(&mnt_path, m, MAXPATHLEN);
+			if (error != 0) {
+				kmem_free(m, MAXPATHLEN);
+				goto error;
+			}
+
+			/*
+			 * If current mnountpoint and vfs_mntpoint are not same,
+			 * store current mountpoint in vfs_mntpoint.
+			 */
+			if (strcmp(zfsvfs->z_vfs->vfs_mntpoint, m) != 0) {
+				kmem_strfree(zfsvfs->z_vfs->vfs_mntpoint);
+				zfsvfs->z_vfs->vfs_mntpoint = kmem_strdup(m);
+			}
+			kmem_free(m, MAXPATHLEN);
+		}
+	}
+
 	/*
 	 * Construct a mount point path from sb of the ctldir inode and dirent
 	 * name, instead of from d_path(), so that chroot'd process doesn't fail