linux-kernel - Re: [PATCH v3] mm/migrate: Fix do_pages

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Message-ID: <aGbAZs4eb8sLT8hj@msg.df7cb.de>
Date: Thu, 3 Jul 2025 19:39:50 +0200
From: Christoph Berg <myon@...ian.org>
To: David Hildenbrand <david@...hat.com>
Cc: Zi Yan <ziy@...dia.com>, Andrew Morton <akpm@...ux-foundation.org>,
	Matthew Brost <matthew.brost@...el.com>,
	Joshua Hahn <joshua.hahnjy@...il.com>, Rakie Kim <rakie.kim@...com>,
	Byungchul Park <byungchul@...com>,
	Gregory Price <gourry@...rry.net>,
	Ying Huang <ying.huang@...ux.alibaba.com>,
	Alistair Popple <apopple@...dia.com>,
	"open list:MEMORY MANAGEMENT - MEMORY POLICY AND MIGRATION" <linux-mm@...ck.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] mm/migrate: Fix do_pages_stat in 32-bit mode

Re: David Hildenbrand
> > For arrays with more than 16 entries, the old code would incorrectly
> > advance the pages pointer by 16 words instead of 16 compat_uptr_t.
> > Fix by doing the pointer arithmetic inside get_compat_pages_array where
> > pages32 is already a correctly-typed pointer.
> > 
> > Discovered while working on PostgreSQL 18's new NUMA introspection code.
> > 
> > Signed-off-by: Christoph Berg <myon@...ian.org>
> > Suggested-by: David Hildenbrand <david@...hat.com>
> > Fixes: 5b1b561ba73c ("mm: simplify compat_sys_move_pages")
> 
> Hmm, still not sure if 5b1b561ba73c really introduced the issue. I think it
> only messed with the "pages" pointer, not with the "status" pointer?

"pages" was the broken one. "status" isn't affected by compat mode.

> Acked-by: David Hildenbrand <david@...hat.com>

Thanks!

Christoph