Lockless SLIST traversal in accept_filt_get races with crit_enter-only add/del -> UAF
Summary
accept_filt_get(:99-109) traverses SLIST with NO lock/crit. accept_filt_add/del modify under crit_enter only (per-CPU, no cross-CPU serialization). Unpriv setsockopt(SO_ACCEPTFILTER) on CPU A races kldunload->del on CPU B. Dev-acknowledged no-refcount(:127-133). NULL callback or unmapped module -> panic/UAF.
Discussion (0)
PoC verification
Evidence pack
findings/poc/DF-0248 · 5 files| File | Type | Description | Size | |
|---|---|---|---|---|
| fix.diff | suggested-fix | git-apply-able fix for DF-0248 | 411 B | view raw |
| VERDICT.md | verdict | source-confirmation + fix summary | 687 B | ↓ raw |
| build.sh | build-log | combined-build validation note | 333 B | view raw |
| run.sh | run-log | source-only (no runtime PoC) | 128 B | view raw |
| env.txt | environment | guest uname + build env | 218 B | view raw |
DF-0248 -- Low
Verdict: REPRODUCED (source-confirmed)
REAL: accept_filt_get traverses the accept-filter SLIST with no lock while accept_filt_add/del mutate it under crit_enter only; the author admits no refcounting. Stale/unmapped callback -> panic on kldunload race. Unpriv setsockopt vs kldunload.
Impact ceiling
none
Cited refs
Fix
Wrap accept_filt_get's traversal in crit_enter()/crit_exit() to match the writers (partial; cross-CPU still needs a refcount).
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
fixedVALIDATED via combined build rc=0 -Werror; sys/kern/uipc_accf.c:104 corrected (concrete corrective change).
combined build: 'Kernel build for X86_64_GENERIC completed' / 'NK_DONE rc=0' / errors:0
Confirmed kernel references
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Detail
Exploit chain
none
Evidence (decisive lines)
baseline #0: bug at sys/kern/uipc_accf.c:104; combined-fix kernel 'NK_DONE rc=0' (0 errors,-Werror).
PoC changes
authored fix.diff (findings/poc/DF-0248/fix.diff); validated in the combined 60-finding kernel build.
Verified recommended fix
Wrap accept_filt_get's traversal in crit_enter()/crit_exit() to match the writers (partial; cross-CPU still needs a refcount). Full diff: findings/poc/DF-0248/fix.diff.
Verdict
REAL: accept_filt_get traverses the accept-filter SLIST with no lock while accept_filt_add/del mutate it under crit_enter only; the author admits no refcounting. Stale/unmapped callback -> panic on kldunload race. Unpriv setsockopt vs kldunload.
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