Differential D52230

random: Fix synchronization of hc_source_mask
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Authored by markj on Aug 28 2025, 9:47 PM.

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rG730b6d166bfe: random: Fix synchronization of hc_source_mask
rGc942d9e83ef1: random: Fix synchronization of hc_source_mask

Summary

This variable provides a mask of all registered entropy sources and is
updated when drivers attach and detach (or by sysctl). However, nothing
was synchronizing accesses to it. Use the harvest lock to provide
mutual exclusion for updates, and use atomic_load_int() to mark unlocked
reads.

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rG FreeBSD src repository

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Event Timeline

markj created this revision.Aug 28 2025, 9:47 PM

Herald added a subscriber: imp. · View Herald TranscriptAug 28 2025, 9:47 PM

markj requested review of this revision.Aug 28 2025, 9:47 PM

Herald added a subscriber: obrien. · View Herald TranscriptAug 28 2025, 9:47 PM

markj added a parent revision: D52229: random: Make the entropy source registration interface more uniform.Aug 28 2025, 9:47 PM

markj added a child revision: D52231: random.4: Document the kern.random.nist_healthtest_enabled tunable.

Harbormaster completed remote builds in B66621: Diff 161155.Aug 28 2025, 9:47 PM

Should we add a comment on the hc_source_mask definition about its locking/access protocol? LGTM.

sys/dev/random/random_harvestq.c
616	We could probably just do a single atomic load on line ~607.
680	Ditto.

This revision is now accepted and ready to land.Aug 28 2025, 11:00 PM

In D52230#1193071, @cem wrote:

Should we add a comment on the hc_source_mask definition about its locking/access protocol? LGTM.

Yeah, I should have done that. Added.

Add a comment above hc_source_mask.
Load the mask once before looping over its bits.

This revision now requires review to proceed.Aug 29 2025, 1:40 PM

Harbormaster completed remote builds in B66633: Diff 161180.Aug 29 2025, 1:40 PM

cem accepted this revision.Aug 29 2025, 4:37 PM

This revision is now accepted and ready to land.Aug 29 2025, 4:37 PM

Closed by commit rGc942d9e83ef1: random: Fix synchronization of hc_source_mask (authored by markj). · Explain WhySep 8 2025, 3:27 PM

This revision was automatically updated to reflect the committed changes.

markj added a commit: rGc942d9e83ef1: random: Fix synchronization of hc_source_mask.

markj added a commit: rG730b6d166bfe: random: Fix synchronization of hc_source_mask.Tue, Sep 30, 3:24 PM

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Path

Size

sys/

dev/

random/

random_harvestq.c

44 lines

Diff 161716

sys/dev/random/random_harvestq.c

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