libext2fs: add sanity check for an invalid itable_used value in inode scan code

[tools/e2fsprogs.git] / lib / ext2fs / inode.c

diff --git a/lib/ext2fs/inode.c b/lib/ext2fs/inode.c
index 573a8fa..a2f2ecd 100644 (file)
--- a/lib/ext2fs/inode.c
+++ b/lib/ext2fs/inode.c
@@ -150,8 +150,11 @@ errcode_t ext2fs_open_inode_scan(ext2_filsys fs, int buffer_blocks,
        scan->blocks_left = scan->fs->inode_blocks_per_group;
        if (EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
                                       EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
-               scan->inodes_left -=
-                       ext2fs_bg_itable_unused(fs, scan->current_group);
+               __u32 unused = ext2fs_bg_itable_unused(fs, scan->current_group);
+               if (scan->inodes_left > unused)
+                       scan->inodes_left -= unused;
+               else
+                       scan->inodes_left = 0;
                scan->blocks_left =
                        (scan->inodes_left +
                         (fs->blocksize / scan->inode_size - 1)) *
@@ -243,8 +246,11 @@ static errcode_t get_next_blockgroup(ext2_inode_scan scan)
        scan->blocks_left = fs->inode_blocks_per_group;
        if (EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
                                       EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
-               scan->inodes_left -=
-                       ext2fs_bg_itable_unused(fs, scan->current_group);
+               __u32 unused = ext2fs_bg_itable_unused(fs, scan->current_group);
+               if (scan->inodes_left > unused)
+                       scan->inodes_left -= unused;
+               else
+                       scan->inodes_left = 0;
                scan->blocks_left =
                        (scan->inodes_left +
                         (fs->blocksize / scan->inode_size - 1)) *