linux-kernel - Re: [PATCH 10/16] mm/hugetlb: update hugetlbfs to use mmap_prepare, mmap

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: <d9121de1-e929-4450-8e19-f1df8b617978@lucifer.local>
Date: Mon, 8 Sep 2025 15:19:53 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        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>,
        David Hildenbrand <david@...hat.com>,
        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
Subject: Re: [PATCH 10/16] mm/hugetlb: update hugetlbfs to use mmap_prepare,
 mmap_complete

On Mon, Sep 08, 2025 at 10:52:40AM -0300, Jason Gunthorpe wrote:
> On Mon, Sep 08, 2025 at 02:37:44PM +0100, Lorenzo Stoakes wrote:
> > On Mon, Sep 08, 2025 at 10:11:21AM -0300, Jason Gunthorpe wrote:
> > > On Mon, Sep 08, 2025 at 12:10:41PM +0100, Lorenzo Stoakes wrote:
> > > > @@ -151,20 +123,55 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
> > > >  		vm_flags |= VM_NORESERVE;
> > > >
> > > >  	if (hugetlb_reserve_pages(inode,
> > > > -				vma->vm_pgoff >> huge_page_order(h),
> > > > -				len >> huge_page_shift(h), vma,
> > > > -				vm_flags) < 0)
> > > > +			vma->vm_pgoff >> huge_page_order(h),
> > > > +			len >> huge_page_shift(h), vma,
> > > > +			vm_flags) < 0) {
> > >
> > > It was split like this because vma is passed here right?
> > >
> > > But hugetlb_reserve_pages() doesn't do much with the vma:
> > >
> > > 	hugetlb_vma_lock_alloc(vma);
> > > [..]
> > > 	vma->vm_private_data = vma_lock;
> > >
> > > Manipulates the private which should already exist in prepare:
> > >
> > > Check non-share a few times:
> > >
> > > 	if (!vma || vma->vm_flags & VM_MAYSHARE) {
> > > 	if (vma && !(vma->vm_flags & VM_MAYSHARE) && h_cg) {
> > > 	if (!vma || vma->vm_flags & VM_MAYSHARE) {
> > >
> > > And does this resv_map stuff:
> > >
> > > 		set_vma_resv_map(vma, resv_map);
> > > 		set_vma_resv_flags(vma, HPAGE_RESV_OWNER);
> > > [..]
> > > 	set_vma_private_data(vma, (unsigned long)map);
> > >
> > > Which is also just manipulating the private data.
> > >
> > > So it looks to me like it should be refactored so that
> > > hugetlb_reserve_pages() returns the priv pointer to set in the VMA
> > > instead of accepting vma as an argument. Maybe just pass in the desc
> > > instead?
> >
> > Well hugetlb_vma_lock_alloc() does:
> >
> > 	vma_lock->vma = vma;
> >
> > Which we cannot do in prepare.
>
> Okay, just doing that in commit would be appropriate then
>
> > This is checked in hugetlb_dup_vma_private(), and obviously desc is not a stable
> > pointer to be used for comparing anything.
> >
> > I'm also trying to do the minimal changes I can here, I'd rather not majorly
> > refactor things to suit this change if possible.
>
> It doesn't look like a bit refactor, pass vma desc into
> hugetlb_reserve_pages(), lift the vma_lock set out

OK, I'll take a look at refactoring this.

>
> Jason

Cheers, Lorenzo