In the Linux kernel, the following vulnerability has been resolved:
erofs: handle NONHEAD !delta[1] lclusters gracefully
syzbot reported a WARNING in iomapiterdone: iomapfiemap+0x73b/0x9b0 fs/iomap/fiemap.c:80 ioctlfiemap fs/ioctl.c:220 [inline]
Generally, NONHEAD lclusters won't have delta[1]==0, except for crafted images and filesystems created by pre-1.0 mkfs versions.
Previously, it would immediately bail out if delta[1]==0, which led to inadequate decompressed lengths (thus FIEMAP is impacted). Treat it as delta[1]=1 to work around these legacy mkfs versions.
lclusterbits > 14
is illegal for compact indexes, error out too.