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
| ||
|
Message-ID: <897590f7-99a5-4053-8566-76623b929c7c@redhat.com> Date: Thu, 5 Jun 2025 14:21:50 +0200 From: David Hildenbrand <david@...hat.com> To: Jason Gunthorpe <jgg@...pe.ca>, Dan Williams <dan.j.williams@...el.com> Cc: Alistair Popple <apopple@...dia.com>, linux-mm@...ck.org, gerald.schaefer@...ux.ibm.com, willy@...radead.org, linux-kernel@...r.kernel.org, nvdimm@...ts.linux.dev, linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org, jhubbard@...dia.com, hch@....de, zhang.lyra@...il.com, debug@...osinc.com, bjorn@...nel.org, balbirs@...dia.com, lorenzo.stoakes@...cle.com, linux-arm-kernel@...ts.infradead.org, loongarch@...ts.linux.dev, linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org, linux-cxl@...r.kernel.org, dri-devel@...ts.freedesktop.org, John@...ves.net Subject: Re: [PATCH 07/12] mm: Remove redundant pXd_devmap calls On 05.06.25 14:09, Jason Gunthorpe wrote: > On Wed, Jun 04, 2025 at 07:35:24PM -0700, Dan Williams wrote: > >> If all dax pages are special, then vm_normal_page() should never find >> them and gup should fail. >> >> ...oh, but vm_normal_page_p[mu]d() is not used in the gup path, and >> 'special' is not set in the pte path. > > That seems really suboptimal?? Why would pmd and pte be different? > >> I think for any p[mu]d where p[mu]d_page() is ok to use should never set >> 'special', right? > > There should be dedicated functions for installing pages and PFNs, > only the PFN one would set the special bit. > > And certainly your tests *should* be failing as special entries should > never ever be converted to struct page. Worth reviewing [1] where I clean that up and describe the current impact. ;) What's even worse about this pte_devmap()/pmd_devmap()/... shit (sorry! but it's absolute shit) is that some pte_mkdev() set the pte special, while others ... don't. E.g., loongarch static inline pte_t pte_mkdevmap(pte_t pte) { pte_val(pte) |= _PAGE_DEVMAP; return pte; } I don't even know how it can (could) survive vm_normal_page(). Of course, a wild (and different) mixture on pmd_mkdevmap() as well. So happy to see that go away. [1] https://lkml.kernel.org/r/20250603211634.2925015-1-david@redhat.com -- Cheers, David / dhildenb
Powered by blists - more mailing lists