hfsplus: don't return 0 when fill_super() failed

syzbot is reporting NULL pointer dereference at mount_fs() [1]. This is because hfsplus_fill_super() is by error returning 0 when hfsplus_fill_super() detected invalid filesystem image, and mount_bdev() is returning NULL because dget(s->s_root) == NULL if s->s_root == NULL, and mount_fs() is accessing root->d_sb because IS_ERR(root) == false if root == NULL. Fix this by returning -EINVAL when hfsplus_fill_super() detected invalid filesystem image. [1] https://syzkaller.appspot.com/bug?id=21acb6850cecbc960c927229e597158cf35f33d0 Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Tetsuo Handa <[email protected]> Reported-by: syzbot <[email protected]> Reviewed-by: Ernesto A. Fernández <[email protected]> Reviewed-by: Andrew Morton <[email protected]> Cc: Al Viro <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
kawasaki · Aug 22, 2018 · 7464726 · 7464726
1 parent c8ed98c
commit 7464726
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/fs/hfsplus/super.c b/fs/hfsplus/super.c
@@ -524,8 +524,10 @@ static int hfsplus_fill_super(struct super_block *sb, void *data, int silent)
 		goto out_put_root;
 	if (!hfs_brec_read(&fd, &entry, sizeof(entry))) {
 		hfs_find_exit(&fd);
-		if (entry.type != cpu_to_be16(HFSPLUS_FOLDER))
+		if (entry.type != cpu_to_be16(HFSPLUS_FOLDER)) {
+			err = -EINVAL;
 			goto out_put_root;
+		}
 		inode = hfsplus_iget(sb, be32_to_cpu(entry.folder.id));
 		if (IS_ERR(inode)) {
 			err = PTR_ERR(inode);