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: stable@kernel.org
Link: https://lore.kernel.org/r/20230506142419.984260-1-tytso@mit.edu
Reported-by: syzbot+394aa8a792cb99dbc837@syzkaller.appspotmail.com
Reported-by: syzbot+344aaa8697ebd232bfc8@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=db56459ea4ac4a676ae4b4678f633e55da005a9b
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: tytso

fs/ext4/hash.c

@@ -277,7 +277,11 @@ static int __ext4fs_dirhash(const struct inode *dir, const char *name, int len,
 	}
 	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

@@ -674,7 +674,7 @@ static struct stats dx_show_leaf(struct inode *dir,
 				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,
@@ -709,8 +709,9 @@ static struct stats dx_show_leaf(struct inode *dir,
 					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));
@@ -720,7 +721,8 @@ static struct stats dx_show_leaf(struct inode *dir,
 #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
@@ -849,8 +851,14 @@ dx_probe(struct ext4_filename *fname, struct inode *dir,
 	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) {
@@ -1111,7 +1119,12 @@ static int htree_dirblock_to_tree(struct file *dir_file,
 				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) &&
@@ -1313,8 +1326,12 @@ static int dx_make_map(struct inode *dir, struct buffer_head *bh,
 		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;
@@ -1452,10 +1469,9 @@ int ext4_fname_setup_ci_filename(struct inode *dir, const struct qstr *iname,
 	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
 
@@ -2298,10 +2314,15 @@ static int make_indexed_dir(handle_t *handle, struct ext4_filename *fname,
 	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;