Unconditional kernel panic if mbuf chain ends with zero-length mbuf
Summary
receive_frame(:1956-1960) for(m=m0;m->m_next;m=m->m_next); if(m->m_len<=0) panic(). XXX comment: lets hope it never happens. Hard panic on malformed input instead of graceful drop. Reachability depends on L2CAP delivering trailing empty mbuf.
Discussion (0)
PoC verification
Evidence pack
findings/poc/DF-0283 · 5 files| File | Type | Description | Size | |
|---|---|---|---|---|
| fix.diff | suggested-fix | git-apply-able fix for DF-0283 | 660 B | view raw |
| VERDICT.md | verdict | source-confirmation + fix summary | 637 B | ↓ raw |
| build.sh | build-log | combined-build validation note | 333 B | view raw |
| run.sh | run-log | source-only (no runtime PoC) | 160 B | view raw |
| env.txt | environment | guest uname + build env | 218 B | view raw |
DF-0283 -- Low
Verdict: REPRODUCED (source-confirmed)
REAL: receive_frame panics ('Empty mbuf at the end of the chain') on a malformed trailing empty mbuf instead of dropping -- a hard kernel panic on bad input. Reachability depends on L2CAP delivering a trailing empty mbuf.
Impact ceiling
panic
Cited refs
Fix
Replace the panic with a graceful drop (NG_FREE_M + return EINVAL).
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/netgraph7/bluetooth/socket/ng_btsocket_rfcomm.c:1958 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/netgraph7/bluetooth/socket/ng_btsocket_rfcomm.c:1958; combined-fix kernel 'NK_DONE rc=0' (0 errors,-Werror).
PoC changes
authored fix.diff (findings/poc/DF-0283/fix.diff); validated in the combined 60-finding kernel build.
Verified recommended fix
Replace the panic with a graceful drop (NG_FREE_M + return EINVAL). Full diff: findings/poc/DF-0283/fix.diff.
Verdict
REAL: receive_frame panics ('Empty mbuf at the end of the chain') on a malformed trailing empty mbuf instead of dropping -- a hard kernel panic on bad input. Reachability depends on L2CAP delivering a trailing empty mbuf.
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