Fix entropy_mutex ownership tracking & re-init race by stenslae · Pull Request #11645 · wolfSSL/wolfssl

stenslae · 2026-10-05T18:35:52Z

Description

Fixed fenrir findings for F-7091, F-7419, and F-8169.

Added boolean tracking on the mutex lock, and made it so mutex locking and stop thread are only called when the current thread successfully acquired the lock. Also changed wc_InitMutex() in Entropy_Init() with wc_local_InitMutexOnce() to prevent re-initalization of an active mutex, and added resetting the atomic entropy flag in Entropy_Final().

Checklist

added tests
updated/added doxygen
updated appropriate READMEs
Updated manual and documentation

github-actions · 2026-10-05T18:39:06Z

MemBrowse Memory Report · Explore what changed →

gcc-arm-cortex-m4

FLASH: .text +64 B (-1.3%, 207,216 B / 262,144 B, total: 79% used)

gcc-arm-cortex-m4-crypto-only

FLASH: -2,796 B (-1.5%, 179,795 B / 262,144 B, total: 69% used)

gcc-arm-cortex-m4-openssl-compat

FLASH: .rodata -2,768 B (-0.3%, 793,436 B / 1,048,576 B, total: 76% used)

gcc-arm-cortex-m4-pkcs7

FLASH: -2,796 B (-1.3%, 220,820 B / 262,144 B, total: 84% used)

gcc-arm-cortex-m4-pq

FLASH: .rodata -2,772 B, .text +64 B (-0.9%, 309,008 B / 1,048,576 B, total: 29% used)

gcc-arm-cortex-m4-rsa-only

FLASH: .rodata -2,768 B (-0.8%, 340,360 B / 1,048,576 B, total: 32% used)

gcc-arm-cortex-m4-tls13

FLASH: .text +64 B (-1.1%, 246,498 B / 262,144 B, total: 94% used)

gcc-arm-cortex-m7

FLASH: .text +64 B (-1.3%, 207,216 B / 262,144 B, total: 79% used)

gcc-arm-cortex-m7-pq

FLASH: .rodata -2,772 B (-0.9%, 309,904 B / 1,048,576 B, total: 30% used)

gcc-arm-cortex-m7-tls13

FLASH: -2,796 B (-1.1%, 246,498 B / 262,144 B, total: 94% used)

stm32-sim-stm32h753

FLASH: .text -2,732 B (-1.3%, 202,988 B / 2,097,152 B, total: 10% used)

No memory changes detected for:

_{Catch memory regressions in CI with MemBrowse. Free for open source.}

Copilot

Copilot review overview

🔵 Needs a closer look

Entropy-source synchronization changes need platform-aware human review and stronger concurrency regression coverage.

Review effort: Balanced
Findings: 2

Open (2)

Add concurrent Entropy_Init regression using real atomic once logic · New
Verify refused entropy locks do not stop another caller's counter · New

What changed in this PR

Hardens wolfCrypt’s memory-based entropy source against mutex ownership and re-initialization errors.

Changes:

Guards mutex release and counter-thread shutdown with ownership tracking.
Uses one-time mutex initialization and resets its flag during finalization.
Adds whitebox lifecycle and failure-path tests.

File	Description
wolfcrypt/src/wolfentropy.c	Updates mutex ownership, initialization, and cleanup handling.
tests/unit-mcdc/test_wolfentropy_whitebox.c	Adds re-initialization, lock-refusal, and held-mutex cleanup checks.

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wolfSSL-Fenrir-bot

Fenrir Automated Review — PR #11645

Scan targets checked: wolfcrypt-src, wolfcrypt-bugs, wolfssl-bugs
Coverage: 2 of 2 in-scope changed file(s) opened by the reviewer

Fenrir result: Approved ✅

No new issues found in the changed files.

Advisory only — this automated result does not count as a GitHub approval.

Review tier: Lite

wolfSSL-Fenrir-bot

Fenrir Automated Review — PR #11645

Scan targets checked: wolfssl-bugs
Unchanged since last review (not re-run): wolfcrypt-src, wolfcrypt-bugs
Coverage: 1 of 1 in-scope changed file(s) opened by the reviewer

Fenrir result: Approved ✅

No new issues found in the changed files.

Advisory only — this automated result does not count as a GitHub approval.

Review tier: Lite

Copilot

Copilot review overview

🟡 Changes recommended

The new on-demand test baseline can falsely report a regression when the threaded entropy counter is stopped.

Review effort: Balanced
Findings: 1

Open (1)

Restart entropy counter before on-demand test to avoid false failures · New

Resolved since last review (2)

Verify refused entropy locks do not stop another caller's counter
Add concurrent Entropy_Init regression using real atomic once logic

wolfSSL-Fenrir-bot

Fenrir Automated Review — PR #11645

Scan targets checked: wolfssl-bugs
Unchanged since last review (not re-run): wolfcrypt-src, wolfcrypt-bugs
Coverage: 1 of 1 in-scope changed file(s) opened by the reviewer

Findings: 1
1 finding(s) posted as inline comments (see file-level comments below)

This review was generated automatically by Fenrir. Reported findings require changes before merge.

Review tier: Lite

Copilot

Note

Copilot was unable to run its full agentic suite in this review.

Copilot review overview

Review effort: Lite
Findings: 5

Open (5)

wb_regress is used as the “real failure” indicator, but the name is ambiguous (it reads like… · New
wb_entropy_get_mutex() reports a skip via WB_NOTE(...) but doesn’t set any flag that affects… · New
In production code, Entropy_StartThread() / Entropy_StopThread() are invoked while holding… · New
Same issue as in wb_entropy_get_mutex(): this early-return “skip” path is not reflected in the… · New
wb_regress is used as the “real failure” indicator, but the name is ambiguous (it reads like… · New

Resolved since last review (1)

Restart entropy counter before on-demand test to avoid false failures

Copilot

🔵 Needs a closer look

Entropy-source synchronization needs platform-specific maintainer validation, and assertion-failure reporting remains unresolved.

1 open finding

Report ownership assertion failures with the recognized failure marker · New

5 resolved since last review

wb_regress is used as the “real failure” indicator, but the name is ambiguous (it reads like…
Same issue as in wb_entropy_get_mutex(): this early-return “skip” path is not reflected in the…
In production code, Entropy_StartThread() / Entropy_StopThread() are invoked while holding…
wb_entropy_get_mutex() reports a skip via WB_NOTE(...) but doesn’t set any flag that affects…
wb_regress is used as the “real failure” indicator, but the name is ambiguous (it reads like…

🧠 Review effort: Balanced

wolfSSL-Fenrir-bot

Fenrir Automated Review — PR #11645

Scan targets checked: wolfssl-bugs
Unchanged since last review (not re-run): wolfcrypt-src, wolfcrypt-bugs
Coverage: 1 of 1 in-scope changed file(s) opened by the reviewer

Findings: 1
1 finding(s) posted as inline comments (see file-level comments below)

This review was generated automatically by Fenrir. Reported findings require changes before merge.

Review tier: Lite

Copilot

🟡 Changes recommended

Initialization readiness can be published before startup completes, allowing a concurrent caller to return success prematurely.

2 open findings

🧠 Review effort: Balanced

wolfSSL-Fenrir-bot

Fenrir Automated Review — PR #11645

Scan targets checked: wolfcrypt-src, wolfcrypt-bugs, wolfssl-bugs
Coverage: 2 of 2 in-scope changed file(s) opened by the reviewer

Fenrir result: Approved ✅

No new issues found in the changed files.

Advisory only — this automated result does not count as a GitHub approval.

Review tier: Lite

lealem47

Looks great @stenslae ! Just a couple of edge case tweaks requested

lealem47 · 2026-10-21T21:32:48Z

        /* Dispose of the SHA3-356 hash object. */
        wc_Sha3_256_Free(&entropyHash);
    #if !defined(SINGLE_THREADED) && !defined(WOLFSSL_MUTEX_INITIALIZER)
        wc_FreeMutex(&entropy_mutex);


Can we free this mutex based on entropy_mutex_init instead of basing it on entropy_memuse_initialized to avoid leaking in the case where the mutex is successfully created but Entropy_Init() ultimately fails?

Sure, changed it so Entropy_Final() now frees the mutex whenever entropy_mutex_init == 2, whether or not init succeeded, and resets the flag to 0 so a later Entropy_Init() re-creates it.

Okay that sounds good. Can you move define ENTROPY_MUTEX_READY 2U to wc_port.h? And use that in wc_local_InitMutexOnce instead of the hard coded 2? Then we can use the same macro in Entropy_Final()

#define WC_MUTEX_READY_ONCE 2U might be a better name if we're making it global

lealem47 · 2026-10-21T22:41:06Z

+/* MemUse entropy global state initialized.  Published with a release store
+ * after all startup work succeeds; checked with an acquire load on the
+ * fast-path so a reader seeing 1 is guaranteed to see a complete init. */
+static wolfSSL_Atomic_Int entropy_memuse_initialized = WOLFSSL_ATOMIC_INITIALIZER(0);


MEDIUM-2: Switching entropy_memuse_initialized from `volatile int` to wolfSSL_Atomic_Int drops volatile in threaded WOLFSSL_NO_ATOMICS builds [SUGGEST] (bug) File: wolfcrypt/src/wolfentropy.c:69-72 Function: (file scope) Confidence: Medium The flag changes from `static volatile int` to `static wolfSSL_Atomic_Int`. In every config where `WOLFSSL_ATOMIC_OPS` gets defined this is a strict improvement (seq_cst load/store, which subsumes the acquire/release the new comments describe). But when no atomic backend matches, `wolfssl/wolfcrypt/wc_port.h:645-653` falls back to `typedef int wolfSSL_Atomic_Int;` with `WOLFSSL_ATOMIC_LOAD(x) (x)` / `WOLFSSL_ATOMIC_STORE(x, val) (x) = (val)` — and that header comment is explicit that it is *not* volatile: "_NO_ATOMICS configs promise no concurrent mutation (single-threaded, or externally serialized)". That promise does not hold here: `HAVE_ENTROPY_MEMUSE` with `!SINGLE_THREADED` is genuinely multi-threaded and the flag is the subject of the double-checked lock in `Entropy_Init()`. Such a build is narrow but real — a threaded target whose compiler matches none of the atomic arms (no `WOLFSSL_USER_DEFINED_ATOMICS`, not BSDKM, no C11 `<stdatomic.h>`, not GNUC `__ATOMIC_SEQ_CST`, not MSVC/Windows — e.g. older IAR/Keil/CC-RX with an RTOS), or any user who sets `WOLFSSL_NO_ATOMICS` in `user_settings.h`. There, the compiler is free to collapse the two `WOLFSSL_ATOMIC_LOAD(entropy_memuse_initialized)` reads in `Entropy_Init()` into one, defeating the re-check that the diff adds — something the old `volatile` prevented. Related: the new comments say "Published with a release store ... checked with an acquire load" and "Release store: publish only after all startup work has succeeded." Those hold under `WOLFSSL_ATOMIC_OPS` but not in the fallback, where the macros carry no ordering at all. Code: -/* MemUse entropy global state initialized. */ -static volatile int entropy_memuse_initialized = 0; +/* MemUse entropy global state initialized. Published with a release store + * after all startup work succeeds; checked with an acquire load on the + * fast-path so a reader seeing 1 is guaranteed to see a complete init. */ +static wolfSSL_Atomic_Int entropy_memuse_initialized = WOLFSSL_ATOMIC_INITIALIZER(0); Recommendation: Either keep `volatile` for the `WOLFSSL_NO_ATOMICS && !SINGLE_THREADED` case, or qualify the new comments to say the acquire/release guarantee applies only when `WOLFSSL_ATOMIC_OPS` is defined (matching how `wc_local_InitMutexOnce()` in wc_port.c:3052 explicitly documents and branches on that distinction). Also note the line is 84 characters, over the project's 80-column convention — wrap the initializer.

Returned that back to using volatile.

… the counter thread or unlocking

stenslae · 2026-10-28T22:10:32Z

@claude review

Copilot

🔵 Needs a closer look

The concurrency- and FIPS-sensitive entropy and mutex lifecycle changes need maintainer runtime validation, since comment-only test updates do not verify concurrent first use, cleanup/reinitialization without static mutex initializers, or counter-thread builds.

No open issues 🎉

1 resolved since last review

Missing executable tests for re-init and internal-failure coverage

_{Review effort: Balanced}

claude

Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.

wolfSSL-Fenrir-bot

Fenrir Automated Review — PR #11645

Scan targets checked: wolfcrypt-src, wolfcrypt-bugs, wolfssl-bugs
Not reviewed (no scan target covers them): doc/dox_comments/header_files/wolfentropy.h
Coverage: 2 of 2 in-scope changed file(s) opened by the reviewer

Findings: 1
1 finding(s) posted as inline comments (see file-level comments below)

This review was generated automatically by Fenrir. Reported findings require changes before merge.

Review tier: Lite

stenslae · 2026-10-28T22:47:34Z

@claude review

Copilot

🟢 Approval recommended

No active review issues are reported for the wolfEntropy mutex-ownership and initialization-race changes.

No open issues 🎉

_{Review effort: Balanced}

wolfSSL-Fenrir-bot

Fenrir Automated Review — PR #11645

Scan targets checked: wolfcrypt-src, wolfcrypt-bugs
Unchanged since last review (not re-run): wolfssl-bugs
Not reviewed (no scan target covers them): doc/dox_comments/header_files/wolfentropy.h
Coverage: 1 of 1 in-scope changed file(s) opened by the reviewer

Fenrir result: Approved ✅

No new issues found in the changed files.

Advisory only — this automated result does not count as a GitHub approval.

Review tier: Lite

Fenrir's latest completed scan found no issues; clearing the prior automated change request.

claude

Code review found no issues

No high-confidence issues detected in this change.

stenslae requested a review from wolfSSL-Fenrir-bot October 5, 2026 18:35

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Emma Stensland added 2 commits October 28, 2026 16:04

F-7091, F-7419, F-8169: track entropy_mutex ownership before stopping…

047da61

… the counter thread or unlocking

Fix Entropy_Init() re-init race

00e748a

stenslae force-pushed the audit-entropy-mutex branch from 5eb688f to 00e748a Compare October 28, 2026 22:10

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Comment thread tests/unit-mcdc/test_wolfentropy_whitebox.c

Start counter thread in wc_Entropy_OnDemandTest()

d374b41

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stenslae assigned lealem47 and unassigned stenslae Oct 28, 2026

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Description

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stenslae commented Oct 28, 2026

stenslae commented Oct 5, 2026 •

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