Integer truncation of uint64_t inf_len to int in udf_read and udf_readdir — files >2GB truncated
Summary
udf_vnops.c:391 int fsize then :396 fsize=node->fentry->inf_len — inf_len is uint64_t (ecma167-udf.h:339) implicitly narrowed to int. Same :673 udf_opendir(node,...,inf_len,...) third arg int fsize. :888 udf_lookup same. For files/dirs >INT_MAX(2GiB) crafted UDF image: fsize truncated wrong loop bounds. Truncated value conservative (smaller not larger) so no memory-safety impact just empty reads/empty dir = DoS/correctness. Fix: use off_t/uint64_t for sizes/offsets throughout.
Discussion (0)
PoC verification
Evidence pack
findings/poc/DF-0833 · 2 files| File | Type | Description | Size | |
|---|---|---|---|---|
| fix.diff | suggested-fix | git-apply-able fix for the cited path | 307 B | view raw |
| VERDICT.md | verdict | source-confirmation narrative | 977 B | ↓ raw |
DF-0833 source-confirmation
Verdict: REPRODUCED (source-confirmed)
Impact: dos Confidence: likely
Kernel ref: sys/vfs/udf/udf_vnops.c:396
Mechanism
uint64 inf_len narrowed to int fsize -> wrong loop bounds for >2GiB UDF files
Confirmation method
Source-trace confirmed the cited code path matches the finding (exact line/condition
verified against sys/). Runtime PoC not exercised for this source-only Low-severity
item; confirmation is by code inspection.
Recommended fix
See fix.diff in this folder (git-apply-able unified diff).
Phase 8 (combined build)
All 64 fixes were batched into one combined patch
(../_batch/combined_64.patch) and applied to in-guest /usr/src. A single
make -j6 nativekernel KERNCONF=X86_64_GENERIC completed rc=0 with 0 errors under
-Werror (../_batch/fix_build.log, 35374 lines). The GENERIC kernel + all modules
(drm, firewire, usb, netgraph, smbfs, fuse, crypto, vm, pmap) compiled clean.
Fix verification
not_testablenot_testable (source-only): no runtime PoC exercised; fix.diff applies cleanly and the combined single nativekernel build of all 64 fixes completed rc=0 with 0 errors under -Werror (findings/poc/_batch/fix_build.log). Bug source-confirmed in baseline tree. Compile-validation of the fix is the requested Phase-8 deliverable for this batch.
combined build: '=== NK_DONE rc=0 ===' and '>>> Kernel build for X86_64_GENERIC completed on Thu Jul 23 09:17:55 UTC 2026' (0 'error:' lines in 35374-line log).
Confirmed kernel references
- s
- y
- s
- /
- v
- f
- s
- /
- u
- d
- f
- /
- u
- d
- f
- _
- v
- n
- o
- p
- s
- .
- c
- :
- 3
- 9
- 6
Detail
Exploit chain
none (non-corruption / source-only confirmation; no memory-corruption escalation chain developed for this Low-severity item)
Evidence (decisive lines)
source-only: uint64 inf_len narrowed to int fsize -> wrong loop bounds for >2GiB UDF files @ sys/vfs/udf/udf_vnops.c:396. Combined fix build: '=== NK_DONE rc=0 ===' / 'Kernel build for X86_64_GENERIC completed', 0 errors under -Werror (findings/poc/_batch/fix_build.log).
PoC changes
authored git-apply-able fix.diff targeting the cited line; source-trace verified the vulnerable path. Evidence pack (VERDICT.md, manifest.json, env.txt, fix.diff) in findings/poc/DF-0833/.
Verified recommended fix
use int64_t fsize instead of narrowing inf_len to int. matches finding proposal. Full diff in findings/poc/DF-0833/fix.diff.
Verdict
REPRODUCED (source-confirmed). Source-trace confirmed uint64 inf_len narrowed to int fsize -> wrong loop bounds for >2GiB UDF files at sys/vfs/udf/udf_vnops.c:396 against the audited sys/ tree; exact line/condition verified.
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