linux-kernel - Re: [PATCHv6 11/17] mm/hugetlb: Remove fake head pages

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

Message-ID: <907ff793-9b02-4a22-a85e-2873246f6402@gmail.com>
Date: Sat, 7 Feb 2026 20:16:25 +0000
From: Usama Arif <usamaarif642@...il.com>
To: Kiryl Shutsemau <kas@...nel.org>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Muchun Song <muchun.song@...ux.dev>, David Hildenbrand <david@...hat.com>,
 Matthew Wilcox <willy@...radead.org>, Frank van der Linden <fvdl@...gle.com>
Cc: Oscar Salvador <osalvador@...e.de>, Mike Rapoport <rppt@...nel.org>,
 Vlastimil Babka <vbabka@...e.cz>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Zi Yan <ziy@...dia.com>,
 Baoquan He <bhe@...hat.com>, Michal Hocko <mhocko@...e.com>,
 Johannes Weiner <hannes@...xchg.org>, Jonathan Corbet <corbet@....net>,
 Huacai Chen <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>,
 Palmer Dabbelt <palmer@...belt.com>, Paul Walmsley
 <paul.walmsley@...ive.com>, Albert Ou <aou@...s.berkeley.edu>,
 Alexandre Ghiti <alex@...ti.fr>, kernel-team@...a.com, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
 loongarch@...ts.linux.dev, linux-riscv@...ts.infradead.org
Subject: Re: [PATCHv6 11/17] mm/hugetlb: Remove fake head pages


> +
>  int __meminit vmemmap_populate_hvo(unsigned long addr, unsigned long end,
>  				       int node, unsigned long headsize)
>  {
> +	unsigned long maddr, len, tail_pfn;
> +	unsigned int order;
>  	pte_t *pte;
> -	unsigned long maddr;
> +
> +	len = end - addr;
> +	order = ilog2(len * sizeof(struct page) / PAGE_SIZE);


This doesnt work for ARM. For len = 32 (2MB contiguous-PTE hugetlb on arm64):
ilog2(32 * 64 / 65536) = ilog2(2048 / 65536) = ilog2(0) which is undefined.

Is order = ilog2(len / sizeof(struct page)) better?



> +	tail_pfn = vmemmap_get_tail(order, node);
> +	if (!tail_pfn)
> +		return -ENOMEM;
>  
>  	for (maddr = addr; maddr < addr + headsize; maddr += PAGE_SIZE) {
>  		pte = vmemmap_populate_address(maddr, node, NULL, -1, 0);
> @@ -398,8 +426,7 @@ int __meminit vmemmap_populate_hvo(unsigned long addr, unsigned long end,
>  	/*
>  	 * Reuse the last page struct page mapped above for the rest.
>  	 */
> -	return vmemmap_populate_range(maddr, end, node, NULL,
> -					pte_pfn(ptep_get(pte)), 0);
> +	return vmemmap_populate_range(maddr, end, node, NULL, tail_pfn, 0);
>  }
>  
>  void __weak __meminit vmemmap_set_pmd(pmd_t *pmd, void *p, int node,