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Differential D26293

Fix a page table pages leak after LA57.
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Authored by kib on Sep 2 2020, 9:23 AM.
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pho

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alc
markj
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rS365251: Fix a page table pages leak after LA57.
Summary

If the call to _pmap_allocpte() is not sleepable, it is possible that allocation of PML4 or PDP page is successful but either PDP or PD page is not. Restructured code _pmap_allocpte() leaves zero-referenced page in the paging structure.

Handle it by checking refcount of the page one level above failed alloc and free that page if its reference count is zero.

Reported and tested by: pho

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rS FreeBSD src repository - subversion
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Event Timeline

kib created this revision.Sep 2 2020, 9:23 AM
Herald added a subscriber: imp. · View Herald TranscriptSep 2 2020, 9:23 AM
kib requested review of this revision.Sep 2 2020, 9:23 AM
Harbormaster completed remote builds in B33323: Diff 76531.Sep 2 2020, 9:23 AM
markj accepted this revision.Sep 2 2020, 2:40 PM
markj added inline comments.
sys/amd64/amd64/pmap.c
4106 ↗(On Diff #76531)

I would call it _unref.

This revision is now accepted and ready to land.Sep 2 2020, 2:40 PM
Closed by commit rS365251: Fix a page table pages leak after LA57. (authored by kib). · Explain WhySep 2 2020, 3:55 PM
This revision was automatically updated to reflect the committed changes.
kib added a commit: rS365251: Fix a page table pages leak after LA57..

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head/
sys/
amd64/
amd64/
23 lines

Diff 76539

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head/sys/amd64/amd64/pmap.c

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