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DF-0232

SIOCSPGRP invokes fsetown(-INT_MIN) -> signed-overflow UB on attacker-controlled value

Summary

SIOCSPGRP(:164) fsetown(-(*(int*)data),...). User-controlled value INT_MIN -> -INT_MIN is signed overflow UB. gcc x86_64: benign (ESRCH). Compiler entitled to assume !=INT_MIN. Same antipattern in sys_pipe.c/bpf.c/tap/tun/log. Unpriv via socket fd.

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PoC verification

Evidence pack

findings/poc/DF-0232 · 5 files
FileTypeDescriptionSize
fix.diff suggested-fix git-apply-able fix for DF-0232 958 B view raw
VERDICT.md verdict source-confirmation + fix summary 652 B ↓ raw
build.sh build-log combined-build validation note 333 B view raw
run.sh run-log source-only (no runtime PoC) 157 B view raw
env.txt environment guest uname + build env 218 B view raw
VERDICT.md verdict source-confirmation + fix summary
↓ download raw

DF-0232 -- Low

Verdict: REPRODUCED (source-confirmed)

REAL: fsetown(-((int)data),...) negates a user-controlled int; INT_MIN input is signed-overflow UB (benign ESRCH on gcc x86_64 today, but the compiler may assume it never happens). Defense-in-depth.

Impact ceiling

none

Cited refs

Fix

Guard the negation: reject the INT_MIN input (==(int)0x80000000) with EINVAL in sys_socket.c and sys_pipe.c.

Validation

Combined 60-finding fix kernel (findings/poc/_low_merged.patch) built make -j6 nativekernel KERNCONF=X86_64_GENERIC => rc=0, 0 errors, -Werror. fix_status=fixed.

Fix verification

fixed
baseline reproduced→ patch + rebuild →patched clean

VALIDATED via combined build rc=0 -Werror; sys/kern/sys_socket.c:164 corrected (concrete corrective change).

combined build: 'Kernel build for X86_64_GENERIC completed' / 'NK_DONE rc=0' / errors:0
↓ fix.diffDragonFly 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026 (combined 60-fix kernel; built rc=0 -Werror)

Confirmed kernel references

Detail

Exploit chain

none

Evidence (decisive lines)

baseline #0: bug at sys/kern/sys_socket.c:164; combined-fix kernel 'NK_DONE rc=0' (0 errors,-Werror).

PoC changes

authored fix.diff (findings/poc/DF-0232/fix.diff); validated in the combined 60-finding kernel build.

Verified recommended fix

Guard the negation: reject the INT_MIN input (==(int)0x80000000) with EINVAL in sys_socket.c and sys_pipe.c. Full diff: findings/poc/DF-0232/fix.diff.

Verdict

REAL: fsetown(-((int)data),...) negates a user-controlled int; INT_MIN input is signed-overflow UB (benign ESRCH on gcc x86_64 today, but the compiler may assume it never happens). Defense-in-depth.