f2fs-tools: ensure that unused xattr space is zeroized

Make fsck.f2fs zeroize the unused xattr space, i.e. the space after the
end of the zero-terminated xattr list, if it isn't already zeroized.

This is important because the kernel currently does not explicitly
zero-terminate the list when writing xattrs.  So, the kernel relies on
the unused space containing zeroes.

Also, add a missing free() to fix a memory leak.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fsck/fsck.c

@@ -834,13 +834,25 @@ void fsck_reada_all_direct_node_blocks(struct f2fs_sb_info *sbi,
 	}
 }
 
+static bool is_zeroed(const u8 *p, size_t size)
+{
+	size_t i;
+
+	for (i = 0; i < size; i++) {
+		if (p[i])
+			return false;
+	}
+	return true;
+}
+
 int chk_extended_attributes(struct f2fs_sb_info *sbi, u32 nid,
 		struct f2fs_node *inode)
 {
 	void *xattr;
 	void *last_base_addr;
 	struct f2fs_xattr_entry *ent;
 	__u32 xattr_size = XATTR_SIZE(&inode->i);
+	bool need_fix = false;
 
 	if (xattr_size == 0)
 		return 0;
@@ -856,18 +868,24 @@ int chk_extended_attributes(struct f2fs_sb_info *sbi, u32 nid,
 			ASSERT_MSG("[0x%x] last xattr entry (offset: %lx) "
 					"crosses the boundary",
 					nid, (long int)((void *)ent - xattr));
-			if (c.fix_on) {
-				memset(ent, 0,
-					(char *)last_base_addr - (char *)ent);
-				write_all_xattrs(sbi, inode, xattr_size, xattr);
-				FIX_MSG("[0x%x] nullify wrong xattr entries",
-						nid);
-				return 1;
-			}
+			need_fix = true;
 			break;
 		}
 	}
-
+	if (!need_fix &&
+	    !is_zeroed((u8 *)ent, (u8 *)last_base_addr - (u8 *)ent)) {
+		ASSERT_MSG("[0x%x] nonzero bytes in xattr space after "
+				"end of list", nid);
+		need_fix = true;
+	}
+	if (need_fix && c.fix_on) {
+		memset(ent, 0, (u8 *)last_base_addr - (u8 *)ent);
+		write_all_xattrs(sbi, inode, xattr_size, xattr);
+		FIX_MSG("[0x%x] nullify wrong xattr entries", nid);
+		free(xattr);
+		return 1;
+	}
+	free(xattr);
 	return 0;
 }