linux-kernel - Re: [PATCH 03/16] mm: add vma_desc_size(), vma_desc

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 for Android: free password hash cracker in your pocket

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

Message-ID: <076658ac-78bc-4d4b-bf3b-d04cd3f0fa21@redhat.com>
Date: Mon, 8 Sep 2025 17:10:20 +0200
From: David Hildenbrand <david@...hat.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: Jonathan Corbet <corbet@....net>, Matthew Wilcox <willy@...radead.org>,
 Guo Ren <guoren@...nel.org>, Thomas Bogendoerfer
 <tsbogend@...ha.franken.de>, Heiko Carstens <hca@...ux.ibm.com>,
 Vasily Gorbik <gor@...ux.ibm.com>, Alexander Gordeev
 <agordeev@...ux.ibm.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>,
 Sven Schnelle <svens@...ux.ibm.com>, "David S . Miller"
 <davem@...emloft.net>, Andreas Larsson <andreas@...sler.com>,
 Arnd Bergmann <arnd@...db.de>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Dan Williams <dan.j.williams@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, Dave Jiang <dave.jiang@...el.com>,
 Nicolas Pitre <nico@...xnic.net>, Muchun Song <muchun.song@...ux.dev>,
 Oscar Salvador <osalvador@...e.de>,
 Konstantin Komarov <almaz.alexandrovich@...agon-software.com>,
 Baoquan He <bhe@...hat.com>, Vivek Goyal <vgoyal@...hat.com>,
 Dave Young <dyoung@...hat.com>, Tony Luck <tony.luck@...el.com>,
 Reinette Chatre <reinette.chatre@...el.com>,
 Dave Martin <Dave.Martin@....com>, James Morse <james.morse@....com>,
 Alexander Viro <viro@...iv.linux.org.uk>,
 Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
 "Liam R . Howlett" <Liam.Howlett@...cle.com>,
 Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
 Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
 Hugh Dickins <hughd@...gle.com>, Baolin Wang
 <baolin.wang@...ux.alibaba.com>, Uladzislau Rezki <urezki@...il.com>,
 Dmitry Vyukov <dvyukov@...gle.com>, Andrey Konovalov <andreyknvl@...il.com>,
 Jann Horn <jannh@...gle.com>, Pedro Falcato <pfalcato@...e.de>,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-fsdevel@...r.kernel.org, linux-csky@...r.kernel.org,
 linux-mips@...r.kernel.org, linux-s390@...r.kernel.org,
 sparclinux@...r.kernel.org, nvdimm@...ts.linux.dev,
 linux-cxl@...r.kernel.org, linux-mm@...ck.org, ntfs3@...ts.linux.dev,
 kexec@...ts.infradead.org, kasan-dev@...glegroups.com,
 Jason Gunthorpe <jgg@...dia.com>
Subject: Re: [PATCH 03/16] mm: add vma_desc_size(), vma_desc_pages() helpers

On 08.09.25 13:10, Lorenzo Stoakes wrote:
> It's useful to be able to determine the size of a VMA descriptor range used
> on f_op->mmap_prepare, expressed both in bytes and pages, so add helpers
> for both and update code that could make use of it to do so.
> 
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> ---
>   fs/ntfs3/file.c    |  2 +-
>   include/linux/mm.h | 10 ++++++++++
>   mm/secretmem.c     |  2 +-
>   3 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ntfs3/file.c b/fs/ntfs3/file.c
> index c1ece707b195..86eb88f62714 100644
> --- a/fs/ntfs3/file.c
> +++ b/fs/ntfs3/file.c
> @@ -304,7 +304,7 @@ static int ntfs_file_mmap_prepare(struct vm_area_desc *desc)
>   
>   	if (rw) {
>   		u64 to = min_t(loff_t, i_size_read(inode),
> -			       from + desc->end - desc->start);
> +			       from + vma_desc_size(desc));
>   
>   		if (is_sparsed(ni)) {
>   			/* Allocate clusters for rw map. */
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index a6bfa46937a8..9d4508b20be3 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3560,6 +3560,16 @@ static inline unsigned long vma_pages(const struct vm_area_struct *vma)
>   	return (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
>   }
>   
> +static inline unsigned long vma_desc_size(struct vm_area_desc *desc)
> +{
> +	return desc->end - desc->start;
> +}
> +
> +static inline unsigned long vma_desc_pages(struct vm_area_desc *desc)
> +{
> +	return vma_desc_size(desc) >> PAGE_SHIFT;
> +}

"const struct vm_area_desc *" in both cases?

> +
>   /* Look up the first VMA which exactly match the interval vm_start ... vm_end */
>   static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm,
>   				unsigned long vm_start, unsigned long vm_end)
> diff --git a/mm/secretmem.c b/mm/secretmem.c
> index 60137305bc20..62066ddb1e9c 100644
> --- a/mm/secretmem.c
> +++ b/mm/secretmem.c
> @@ -120,7 +120,7 @@ static int secretmem_release(struct inode *inode, struct file *file)
>   
>   static int secretmem_mmap_prepare(struct vm_area_desc *desc)
>   {
> -	const unsigned long len = desc->end - desc->start;
> +	const unsigned long len = vma_desc_size(desc);
>   
>   	if ((desc->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
>   		return -EINVAL;

We really want to forbid any private mappings here, independent of cow.

Maybe a is_private_mapping() helper

or a

vma_desc_is_private_mapping()

helper if we really need it

-- 
Cheers

David / dhildenb