vm_fault: Fix a racy copy of page valid bits
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Authored by markj on Jun 13 2022, 3:49 PM.

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Reviewers

alc
kib

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rGd0443e2b9832: vm_fault: Fix a racy copy of page valid bits

Summary

We do not hold the object lock or a page busy lock when copying src_m's
validity state. Prior to commit 45d72c7d7fca we marked dst_m as fully
valid.

Use the source object's read lock to ensure that valid bits are not
concurrently cleared.

Noticed during code inspection.

Fixes: 45d72c7d7fca ("vm_fault_copy_entry: accept invalid source pages.")

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Repository

rG FreeBSD src repository

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Event Timeline

markj created this revision.Jun 13 2022, 3:49 PM

Herald added a subscriber: imp. · View Herald TranscriptJun 13 2022, 3:49 PM

markj requested review of this revision.Jun 13 2022, 3:49 PM

Harbormaster completed remote builds in B45956: Diff 106865.Jun 13 2022, 3:49 PM

markj added a parent revision: D35470: vm: Fix racy checks for swap objects.Jun 13 2022, 3:49 PM

kib accepted this revision.Jun 13 2022, 7:15 PM

This revision is now accepted and ready to land.Jun 13 2022, 7:15 PM

alc accepted this revision.Jun 14 2022, 5:41 PM

alc added inline comments.Jun 14 2022, 5:44 PM

sys/vm/vm_fault.c
2139–2142	I would also suggest moving the WUNLOCK/WLOCK inside this "if" statement,

markj marked an inline comment as done.Jun 14 2022, 6:09 PM

markj added inline comments.

sys/vm/vm_fault.c
2139–2142	Done in D35485

Closed by commit rGd0443e2b9832: vm_fault: Fix a racy copy of page valid bits (authored by markj). · Explain WhyJun 14 2022, 10:19 PM

This revision was automatically updated to reflect the committed changes.

markj marked an inline comment as done.

markj added a commit: rGd0443e2b9832: vm_fault: Fix a racy copy of page valid bits.

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sys/

vm/

vm_fault.c

9 lines

Diff 106935

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vm_fault: Fix a racy copy of page valid bitsClosedPublicActions