NetBSD Problem Report #60233

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Date: Thu,  7 May 2026 05:56:05 +0000 (UTC)
From: thorpej@me.com
Reply-To: thorpej@me.com
To: gnats-bugs@NetBSD.org
Subject: UVM does not seem to initialize mod/ref state for a freshly-allocated page
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X-From4GNATS: "thorpej@me.com via gnats" <gnats-admin@NetBSD.org>

>Number:         60233
>Category:       kern
>Synopsis:       UVM does not seem to initialize mod/ref state for a freshly-allocated page
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu May 07 06:00:00 +0000 2026
>Originator:     Jason Thorpe
>Release:        NetBSD 11 and later
>Organization:
Society for Aspiring Unix Grey-beards
>Environment:
This is a generic problem
>Description:
UVM seems to not initialize the mod/ref state for a page freshly pulled from a page free list.  Of course, this page was free, and so the mod/ref state should be pristine.

It stands to reason that such a page should start out with mod and ref being false.  Perhaps this gets harmonized later once the page is part of a ZFOD or a page-in or something.  But I thought I'd file this PR so that I don't forget to at least bring it up at some point.
>How-To-Repeat:
N/A
>Fix:
N/A

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