KaraZajac
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Promotes refluxfs (CVE-2026-64600) to a 🟢 full-chain module. VM-verified end-to-end on Rocky Linux 9.8 / 5.14.0-687.10.1.el9_8.0.1.x86_64 under qemu/KVM, unprivileged uid=1000, SELinux Enforcing: skeletonkey --exploit refluxfs --i-know --full-chain reflink-clones /etc/passwd, races the CoW window (32 writers / 8 helpers), strips root's password field on-disk (root❌ -> root::, the public PoC's technique), evicts the stale page cache, verifies via O_DIRECT and returns EXPLOIT_OK. `su root` (empty password) then gives uid 0. 3/3 wins on a private-extent target (1244/3716/7913 rounds, 4-30s). Safety properties (this bug rewrites the block device permanently, unlike the page-cache 🟢 modules): - Crafts the payload FIRST and refuses unless it can preserve both root and the invoking user's line; every other passwd line is kept byte-for-byte. A tail-truncating port drops sshd/nobody/the caller and bricks login (hit exactly this during development). - Backs /etc/passwd up before the race; restores on failure; cleanup() restores it (run as root after the pop). - Destructive path gated behind --full-chain. Plain --exploit / --auto run only the safe own-files trigger (EXPLOIT_FAIL), unchanged. Exploitability constraint discovered during verification (NOT in the Qualys writeup): the race only fires when the target's extent is PRIVATE going in. The block starts at refcount 2 (target + attacker clone), the concurrent CoW drops it to 1, and the stale writer reads "1 -> private". A file already reflink-shared with a third file keeps a post-CoW refcount > 1 and is NOT attackable via that target. Stock Rocky 9 ships /etc/passwd pre-shared and was unattackable across ~41,000 rounds; rewriting it to a private extent (byte-identical content, as any useradd/passwd/vipw does) made it fall in ~2,000 rounds. So the exploitable state is the normal administered state. Also fixed a page-cache staleness bug in the win path: the overwrite bypasses the target inode, so its clean cached pages are never invalidated and a buffered read (getpwnam in `su`, or the module's own verify) would see the OLD passwd. The module now issues POSIX_FADV_DONTNEED on a win and verifies via O_DIRECT. detect() --active gains a per-target extent-privacy check: it reports whether /etc/passwd is private (attackable) or already-shared (not). 88-test unit harness still green (148 total). Docs updated: MODULE.md (full-chain flow, private-extent precondition, verification tables), NOTICE.md, CVES.md (🟢 + tier/ops tables), README (15 full-chain / 13 primitive; lands-root list), RELEASE_NOTES, targets.yaml. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_0118iUgHY44hdRtANgyCmu7y
