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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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Details

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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rG FreeBSD src repository
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Event Timeline

markj requested review of this revision.Jun 13 2022, 3:49 PM
This revision is now accepted and ready to land.Jun 13 2022, 7:15 PM
sys/vm/vm_fault.c
2139–2142

I would also suggest moving the WUNLOCK/WLOCK inside this "if" statement,

markj added inline comments.
sys/vm/vm_fault.c
2139–2142

Done in D35485

This revision was automatically updated to reflect the committed changes.
markj marked an inline comment as done.