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Differential D35471

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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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.")

Diff Detail

Repository
rS FreeBSD src repository - subversion
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Buildable 45956
Build 42844: arc lint + arc unit

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
2149–2152

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
2149–2152

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.

Revision Contents
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PathSize
sys/
vm/
9 lines

Diff 106865

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sys/vm/vm_fault.c

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