staging: erofs: some compressed cluster should be submitted for corrupted images

commit ee45197c upstream.

As reported by erofs_utils fuzzer, a logical page can belong
to at most 2 compressed clusters, if one compressed cluster
is corrupted, but the other has been ready in submitting chain.

The chain needs to submit anyway in order to keep the page
working properly (page unlocked with PG_error set, PG_uptodate
not set).

Let's fix it now.

Fixes: 3883a79a ("staging: erofs: introduce VLE decompression support")
Cc: <stable@vger.kernel.org> # 4.19+
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20190819103426.87579-2-gaoxiang25@huawei.com
[ Gao Xiang: Manually backport to v4.19.y stable. ]
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/erofs/unzip_vle.c

@@ -1335,19 +1335,18 @@ static int z_erofs_vle_normalaccess_readpage(struct file *file,
 	err = z_erofs_do_read_page(&f, page, &pagepool);
 	(void)z_erofs_vle_work_iter_end(&f.builder);
 
-	if (err) {
+	/* if some compressed cluster ready, need submit them anyway */
+	z_erofs_submit_and_unzip(&f, &pagepool, true);
+
+	if (err)
 		errln("%s, failed to read, err [%d]", __func__, err);
-		goto out;
-	}
 
-	z_erofs_submit_and_unzip(&f, &pagepool, true);
-out:
 	if (f.m_iter.mpage != NULL)
 		put_page(f.m_iter.mpage);
 
 	/* clean up the remaining free pages */
 	put_pages_list(&pagepool);
-	return 0;
+	return err;
 }
 
 static inline int __z_erofs_vle_normalaccess_readpages(