ext4: improve error handling from ext4_dirhash()

The ext4_dirhash() will *almost* never fail, especially when the hash
tree feature was first introduced. However, with the addition of
support of encrypted, casefolded file names, that function can most
certainly fail today.

So make sure the callers of ext4_dirhash() properly check for
failures, and reflect the errors back up to their callers.

Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Reported-by: [e-mail]
Reported-by: [e-mail]
Link: https://syzkaller.appspot.com/bug?id=db56459ea4ac4a676ae4b4678f633e55da005a9b
Signed-off-by: Theodore Ts'o <[e-mail]>

fs/ext4/hash.c

···
 	}
 	default:
 		hinfo->hash = 0;
-		return -1;
+		hinfo->minor_hash = 0;
+		ext4_warning(dir->i_sb,
+			     "invalid/unsupported hash tree version %u",
+			     hinfo->hash_version);
+		return -EINVAL;
 	}
 	hash = hash & ~1;
 	if (hash == (EXT4_HTREE_EOF_32BIT << 1))

fs/ext4/namei.c

···
 				len = de->name_len;
 				if (!IS_ENCRYPTED(dir)) {
 					/* Directory is not encrypted */
-					ext4fs_dirhash(dir, de->name,
+					(void) ext4fs_dirhash(dir, de->name,
 						de->name_len, &h);
 					printk("%*.s:(U)%x.%u ", len,
 					       name, h.hash,
···
 					if (IS_CASEFOLDED(dir))
 						h.hash = EXT4_DIRENT_HASH(de);
 					else
-						ext4fs_dirhash(dir, de->name,
-						       de->name_len, &h);
+						(void) ext4fs_dirhash(dir,
+							de->name,
+							de->name_len, &h);
 					printk("%*.s:(E)%x.%u ", len, name,
 					       h.hash, (unsigned) ((char *) de
 								   - base));
···
 #else
 				int len = de->name_len;
 				char *name = de->name;
-				ext4fs_dirhash(dir, de->name, de->name_len, &h);
+				(void) ext4fs_dirhash(dir, de->name,
+						      de->name_len, &h);
 				printk("%*.s:%x.%u ", len, name, h.hash,
 				       (unsigned) ((char *) de - base));
 #endif
···
 	hinfo->seed = EXT4_SB(dir->i_sb)->s_hash_seed;
 	/* hash is already computed for encrypted casefolded directory */
 	if (fname && fname_name(fname) &&
-				!(IS_ENCRYPTED(dir) && IS_CASEFOLDED(dir)))
-		ext4fs_dirhash(dir, fname_name(fname), fname_len(fname), hinfo);
+	    !(IS_ENCRYPTED(dir) && IS_CASEFOLDED(dir))) {
+		int ret = ext4fs_dirhash(dir, fname_name(fname),
+					 fname_len(fname), hinfo);
+		if (ret < 0) {
+			ret_err = ERR_PTR(ret);
+			goto fail;
+		}
+	}
 	hash = hinfo->hash;
 
 	if (root->info.unused_flags & 1) {
···
 				hinfo->minor_hash = 0;
 			}
 		} else {
-			ext4fs_dirhash(dir, de->name, de->name_len, hinfo);
+			err = ext4fs_dirhash(dir, de->name,
+					     de->name_len, hinfo);
+			if (err < 0) {
+				count = err;
+				goto errout;
+			}
 		}
 		if ((hinfo->hash < start_hash) ||
 		    ((hinfo->hash == start_hash) &&
···
 		if (de->name_len && de->inode) {
 			if (ext4_hash_in_dirent(dir))
 				h.hash = EXT4_DIRENT_HASH(de);
-			else
-				ext4fs_dirhash(dir, de->name, de->name_len, &h);
+			else {
+				int err = ext4fs_dirhash(dir, de->name,
+						     de->name_len, &h);
+				if (err < 0)
+					return err;
+			}
 			map_tail--;
 			map_tail->hash = h.hash;
 			map_tail->offs = ((char *) de - base)>>2;
···
 	hinfo->hash_version = DX_HASH_SIPHASH;
 	hinfo->seed = NULL;
 	if (cf_name->name)
-		ext4fs_dirhash(dir, cf_name->name, cf_name->len, hinfo);
+		return ext4fs_dirhash(dir, cf_name->name, cf_name->len, hinfo);
 	else
-		ext4fs_dirhash(dir, iname->name, iname->len, hinfo);
-	return 0;
+		return ext4fs_dirhash(dir, iname->name, iname->len, hinfo);
 }
 #endif
 
···
 	fname->hinfo.seed = EXT4_SB(dir->i_sb)->s_hash_seed;
 
 	/* casefolded encrypted hashes are computed on fname setup */
-	if (!ext4_hash_in_dirent(dir))
-		ext4fs_dirhash(dir, fname_name(fname),
-				fname_len(fname), &fname->hinfo);
-
+	if (!ext4_hash_in_dirent(dir)) {
+		int err = ext4fs_dirhash(dir, fname_name(fname),
+					 fname_len(fname), &fname->hinfo);
+		if (err < 0) {
+			brelse(bh2);
+			brelse(bh);
+			return err;
+		}
+	}
 	memset(frames, 0, sizeof(frames));
 	frame = frames;
 	frame->entries = entries;