OOB read in PAP ACK/NAK debug: wrong bound len+4 should be len-4
Summary
PAP_ACK(:4390) and PAP_NAK(:4426) debug: name_len<len+4 guard should be name_len<len-4. name at offset 5, name_len at offset 4. Off by 8. sppp_print_string walks past valid mbuf data -> stale bytes to syslog. IFF_DEBUG only.
Discussion (0)
PoC verification
Evidence pack
findings/poc/DF-0270 · 5 files| File | Type | Description | Size | |
|---|---|---|---|---|
| fix.diff | suggested-fix | git-apply-able fix for DF-0270 | 633 B | view raw |
| VERDICT.md | verdict | source-confirmation + fix summary | 613 B | ↓ raw |
| build.sh | build-log | combined-build validation note | 333 B | view raw |
| run.sh | run-log | source-only (no runtime PoC) | 170 B | view raw |
| env.txt | environment | guest uname + build env | 218 B | view raw |
DF-0270 -- Low
Verdict: REPRODUCED (source-confirmed)
REAL: PAP_ACK/PAP_NAK debug guard is name_len < len+4 but should be name_len < len-4 (name at offset 5, name_len at offset 4) -- off by 8; sppp_print_string walks past valid mbuf data -> stale bytes to syslog. IFF_DEBUG only.
Impact ceiling
none
Cited refs
Fix
Fix both sites: len+4 -> len-4.
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/net/sppp/if_spppsubr.c:4390 corrected (concrete corrective change).
combined build: 'Kernel build for X86_64_GENERIC completed' / 'NK_DONE rc=0' / errors:0
Confirmed kernel references
- s
- y
- s
- /
- n
- e
- t
- /
- s
- p
- p
- p
- /
- i
- f
- _
- s
- p
- p
- p
- s
- u
- b
- r
- .
- c
- :
- 4
- 3
- 9
- 0
- s
- y
- s
- /
- n
- e
- t
- /
- s
- p
- p
- p
- /
- i
- f
- _
- s
- p
- p
- p
- s
- u
- b
- r
- .
- c
- :
- 4
- 4
- 2
- 6
Detail
Exploit chain
none
Evidence (decisive lines)
baseline #0: bug at sys/net/sppp/if_spppsubr.c:4390; combined-fix kernel 'NK_DONE rc=0' (0 errors,-Werror).
PoC changes
authored fix.diff (findings/poc/DF-0270/fix.diff); validated in the combined 60-finding kernel build.
Verified recommended fix
Fix both sites: len+4 -> len-4. Full diff: findings/poc/DF-0270/fix.diff.
Verdict
REAL: PAP_ACK/PAP_NAK debug guard is name_len < len+4 but should be name_len < len-4 (name at offset 5, name_len at offset 4) -- off by 8; sppp_print_string walks past valid mbuf data -> stale bytes to syslog. IFF_DEBUG only.
No comments yet.