linux-kernel - Re: [PATCH 0/3] mm: treewide: make get_free

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <aPT0zNMZqt89cIXH@kernel.org>
Date: Sun, 19 Oct 2025 17:25:16 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Matthew Wilcox <willy@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Brendan Jackman <jackmanb@...gle.com>,
	David Hildenbrand <david@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Julia Lawall <Julia.Lawall@...ia.fr>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Michal Hocko <mhocko@...e.com>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Vlastimil Babka <vbabka@...e.cz>, Zi Yan <ziy@...dia.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 0/3] mm: treewide: make get_free_pages() and return void *

On Sun, Oct 19, 2025 at 01:30:47AM +0100, Matthew Wilcox wrote:
> On Sat, Oct 18, 2025 at 12:29:59PM +0300, Mike Rapoport wrote:
> > Vast majority of allocations that use get_free_pages() and its derivatives
> > cast the returned unsigned long to a pointer and then cast it back to
> > unsigned long when freeing the memory.
> > 
> > These castings are useless and only obfuscate the code.
> > 
> > Make get_free_pages() and friends return 'void *' and free_pages() accept
> > 'void *' as its address parameter.
> 
> No.  Linus has rejected this change before.  I can't find it now, it was
> a long time ago. 

If it was a long time ago, he might not object it now.

> Most of them shouldn't be using get_free_pages() at all, they should be
> using kmalloc().

Don't know if most but some of them could. Still, we'd have a bunch of
get_free_pages() users with needless castings.
And converting callers that should use kmalloc() is a long and tedious
process, while here we get an API improvement in a single automated change.

-- 
Sincerely yours,
Mike.