From ad9ac6d07ce1819260c2b7f090fd4fe742c80d9f Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Sun, 10 Jul 2022 23:49:07 -0600
Subject: Fuzz btrfsitem, and by consequence improve binstruct errors

---
 lib/btrfs/btrfsitem/item_dir.go | 50 ++++++++++++++---------------------------
 1 file changed, 17 insertions(+), 33 deletions(-)

(limited to 'lib/btrfs/btrfsitem/item_dir.go')

diff --git a/lib/btrfs/btrfsitem/item_dir.go b/lib/btrfs/btrfsitem/item_dir.go
index 859cd14..2fb2d41 100644
--- a/lib/btrfs/btrfsitem/item_dir.go
+++ b/lib/btrfs/btrfsitem/item_dir.go
@@ -9,47 +9,21 @@ import (
 	"hash/crc32"
 
 	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
+	"git.lukeshu.com/btrfs-progs-ng/lib/binstruct/binutil"
 	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/internal"
 )
 
-// key.objectid = inode of directory containing this entry
-// key.offset =
-//    for DIR_ITEM and XATTR_ITEM = NameHash(name)
-//    for DIR_INDEX               = index id in the directory (starting at 2, because "." and "..")
-type DirEntries []DirEntry // DIR_ITEM=84 DIR_INDEX=96 XATTR_ITEM=24
+const MaxNameLen = 255
 
 func NameHash(dat []byte) uint64 {
 	return uint64(^crc32.Update(1, crc32.MakeTable(crc32.Castagnoli), dat))
 }
 
-func (o *DirEntries) UnmarshalBinary(dat []byte) (int, error) {
-	*o = nil
-	n := 0
-	for n < len(dat) {
-		var ref DirEntry
-		_n, err := binstruct.Unmarshal(dat, &ref)
-		n += _n
-		if err != nil {
-			return n, err
-		}
-		*o = append(*o, ref)
-	}
-	return n, nil
-}
-
-func (o DirEntries) MarshalBinary() ([]byte, error) {
-	var ret []byte
-	for _, ref := range o {
-		bs, err := binstruct.Marshal(ref)
-		ret = append(ret, bs...)
-		if err != nil {
-			return ret, err
-		}
-	}
-	return ret, nil
-}
-
-type DirEntry struct {
+// key.objectid = inode of directory containing this entry
+// key.offset =
+//    for DIR_ITEM and XATTR_ITEM = NameHash(name)
+//    for DIR_INDEX               = index id in the directory (starting at 2, because "." and "..")
+type DirEntry struct { // DIR_ITEM=84 DIR_INDEX=96 XATTR_ITEM=24
 	Location      internal.Key `bin:"off=0x0, siz=0x11"`
 	TransID       int64        `bin:"off=0x11, siz=8"`
 	DataLen       uint16       `bin:"off=0x19, siz=2"` // [ignored-when-writing]
@@ -61,10 +35,20 @@ type DirEntry struct {
 }
 
 func (o *DirEntry) UnmarshalBinary(dat []byte) (int, error) {
+	if err := binutil.NeedNBytes(dat, 0x1e); err != nil {
+		return 0, err
+	}
 	n, err := binstruct.UnmarshalWithoutInterface(dat, o)
 	if err != nil {
 		return n, err
 	}
+	if o.NameLen > MaxNameLen {
+		return 0, fmt.Errorf("maximum name len is %v, but .NameLen=%v",
+			MaxNameLen, o.NameLen)
+	}
+	if err := binutil.NeedNBytes(dat, 0x1e+int(o.DataLen)+int(o.NameLen)); err != nil {
+		return 0, err
+	}
 	o.Data = dat[n : n+int(o.DataLen)]
 	n += int(o.DataLen)
 	o.Name = dat[n : n+int(o.NameLen)]
-- 
cgit v1.2.3-2-g168b