KaraZajac
e46a32f11e
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Adds the corpus's first XFS module and its first data-oriented kernel bug —
every other kernel entry corrupts memory; this one corrupts file contents.
xfs_direct_write_iomap_begin() reads the data-fork extent map under ILOCK,
then xfs_reflink_fill_cow_hole() drops ILOCK to wait for transaction log
space. On reacquiring it, the code re-queries the refcount btree at the
ORIGINAL imap->br_startblock and never re-reads the data fork. A second
O_DIRECT writer holding only IOLOCK completes a whole CoW cycle in that
window, so the first writer's stale mapping sees refcount 1, treats a
still-shared block as private, and writes to it in place — landing its data
on the reflink source file's on-disk blocks.
The primitive is an arbitrary overwrite of the on-disk contents of any
readable file, which has three consequences that drive the design:
- No offsets, no ROP, no KASLR/SMEP/SMAP; SELinux, containers and seccomp
are all irrelevant.
- The victim's inode is never written, so mtime/ctime/size never change
and nothing is logged — FIM and `-w /etc/passwd -p wa` cannot see it.
- The change persists across reboots.
Introduced 4.11 (3c68d44a2b49); fixed 2f4acd0fcd86 (mainline 7.2-rc4,
merged 2026-07-16), stable backports 7.1.4 / 6.18.39 / 6.12.96. Exposure is
distro-shaped: RHEL/CentOS/Rocky/Alma/Oracle/CloudLinux 8-10, Fedora Server
>= 31 and Amazon Linux 2023 ship XFS+reflink by default.
detect() is not a pure version gate — reachability here is safely
observable, so it pairs the backport table with a real storage precondition
(writable XFS via statfs XFS_SUPER_MAGIC, deliberately not via a successful
FICLONE since btrfs implements that too and is unaffected). --active
confirms reflink via FICLONE; SKELETONKEY_XFS_ASSUME_REFLINK=1/0 overrides.
On rpm-family hosts it warns that vendors backport without bumping the
upstream version, so the verdict speaks only to the upstream base.
exploit() forks a child that works only in a private mkdtemp scratch dir on
two files it owns: it establishes a shared extent (FICLONE, corroborated by
FIEMAP_EXTENT_SHARED) plus an O_DIRECT gate, then races a hard-bounded
8 writers / 2 helpers / 16 rounds / 2s and stops, reading the donor back
with O_DIRECT. Deliberately under-driven, and it never clones or targets a
file it does not own — the /etc/passwd overwrite -> su -> root step is
documented but NOT bundled. Always returns EXPLOIT_FAIL.
Safety rank 55, far above bad_epoll (12) and ghostlock (11): a won race
corrupts 4 KiB of our own scratch file and cannot touch kernel memory, so
there is no oops/KASAN/panic path.
Detection inverts the usual advice. auditd/sigma anchor on ioctl request
0x40049409 (FICLONE, matched exactly) and openat O_DIRECT; falco adds the
cross-uid reflink condition; and the yara rule is genuinely the right tool
here, matching the on-disk artifact because FIM is structurally blind.
VM-VERIFIED 2026-07-23 — the corpus's first rpm-family verification, taking
the empirical count to 29 of 41 CVEs. Rocky Linux 9.8 /
5.14.0-687.10.1.el9_8.0.1.x86_64 under qemu/KVM, stock GenericCloud layout
with no provisioner changes (root is XFS with reflink=1 out of the box).
detect() -> VULNERABLE, --active FICLONE witness confirmed reflink, phase A
observed FIEMAP_EXTENT_SHARED on a real shared extent, scratch self-cleaned,
clean build on el9 gcc. The underlying bug was separately confirmed winnable
on that kernel via tools/verify-vm/refluxfs_verify.c at the public PoC's
parameters (32 writers / 8 helpers, 60s): 4/4 runs won, first divergence
after 69/114/170/494 rounds. The shipped under-driven trigger did NOT win in
its 2s budget on that same vulnerable kernel — intended behaviour, and
exactly why a non-win must never be read as "patched".
14 new detect() unit rows (148 tests total, 0 failures). Bumps to v0.9.14.
Credit: Qualys Threat Research Unit (blog by Saeed Abbasi; the technical
advisory credits model-assisted kernel analysis performed with Anthropic),
and the upstream XFS maintainers who fixed it.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0118iUgHY44hdRtANgyCmu7y
62 lines
2.3 KiB
C
62 lines
2.3 KiB
C
/*
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* SKELETONKEY — canonical "register every module family" enumeration.
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*
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* Kept in its own translation unit so registry.c stays standalone:
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* the kernel_range unit-test binary links registry.c (for the basic
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* register / count / find API) without pulling in every module's
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* symbol. The main binary and detect-integration test link this
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* file too and get the full lineup.
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*
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* Adding a new module is one new register_<family>() declaration in
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* registry.h plus one call below — the integration test picks it up
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* via skeletonkey_register_all_modules() in its main().
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*/
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#include "registry.h"
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void skeletonkey_register_all_modules(void)
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{
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skeletonkey_register_copy_fail_family();
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skeletonkey_register_dirty_pipe();
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skeletonkey_register_entrybleed();
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skeletonkey_register_pwnkit();
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skeletonkey_register_nf_tables();
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skeletonkey_register_overlayfs();
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skeletonkey_register_cls_route4();
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skeletonkey_register_dirty_cow();
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skeletonkey_register_ptrace_traceme();
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skeletonkey_register_netfilter_xtcompat();
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skeletonkey_register_af_packet();
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skeletonkey_register_fuse_legacy();
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skeletonkey_register_stackrot();
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skeletonkey_register_af_packet2();
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skeletonkey_register_cgroup_release_agent();
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skeletonkey_register_overlayfs_setuid();
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skeletonkey_register_nft_set_uaf();
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skeletonkey_register_af_unix_gc();
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skeletonkey_register_nft_fwd_dup();
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skeletonkey_register_nft_payload();
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skeletonkey_register_sudo_samedit();
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skeletonkey_register_sequoia();
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skeletonkey_register_sudoedit_editor();
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skeletonkey_register_vmwgfx();
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skeletonkey_register_dirtydecrypt();
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skeletonkey_register_fragnesia();
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skeletonkey_register_pack2theroot();
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skeletonkey_register_sudo_chwoot();
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skeletonkey_register_udisks_libblockdev();
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skeletonkey_register_pintheft();
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skeletonkey_register_mutagen_astronomy();
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skeletonkey_register_sudo_runas_neg1();
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skeletonkey_register_tioscpgrp();
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skeletonkey_register_vsock_uaf();
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skeletonkey_register_nft_pipapo();
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skeletonkey_register_ptrace_pidfd();
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skeletonkey_register_sudo_host();
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skeletonkey_register_cifswitch();
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skeletonkey_register_nft_catchall();
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skeletonkey_register_bad_epoll();
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skeletonkey_register_ghostlock();
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skeletonkey_register_refluxfs();
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}
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