fix(vfs): saturate/checked XFS extent and inode-offset arithmetic#134
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Crafted XFS on-disk fields can overflow u64 (overflow-checks ON = ring-0 halt) in the inode/extent translation helpers: - XfsExtent/XfsInodeExtent::contains: startoff + blockcount, where startoff is an unmasked 64-bit on-disk value that can sit near u64::MAX. Use saturating_add. - XfsMount::inode_offset: ag * sb_agblocks * sb_blocksize (+ local * sb_inodesize) is a three-way product of parsed inode-number and superblock-geometry values. Use checked_mul/checked_add and reject with InvalidArgument on overflow. - XfsExtentRec::last_off: startoff + blockcount - 1 underflows for an empty extent (blockcount == 0). Use saturating_sub.
kernalix7
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Jun 23, 2026
…hmetic (#135) Sibling sites to #134 (same parsed-byte overflow class, found by a subsystem-wide sweep): - xfs.rs read_ag_headers: i * sb_agblocks * sb_blocksize (+ sb_sectsize) is the same three-way product of parsed superblock geometry as inode_offset; a crafted superblock overflows it during mount. Saturate so an out-of-range AG offset fails the read instead of panicking. - xfs_inode.rs XfsExtent::end_offset: startoff + blockcount mirrors the contains() overflow fixed in #134. Use saturating_add.
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Crafted XFS on-disk fields can overflow u64 (overflow-checks ON = ring-0 halt):
XfsExtent/XfsInodeExtent::contains:startoff + blockcountwith unmasked 64-bitstartoffnear u64::MAX → saturating_add.XfsMount::inode_offset:ag * sb_agblocks * sb_blocksize (+ local * sb_inodesize)three-way product of parsed values → checked_mul/checked_add, reject InvalidArgument on overflow.XfsExtentRec::last_off:startoff + blockcount - 1underflows for an empty extent → saturating_sub.Found by an opencode/glm-5.2 agentic lane; verified + sibling-swept by hand.