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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id i65-20020a819144000000b0057072e7fa77sm637283ywg.95.2023.07.11.09.13.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Jul 2023 09:13:34 -0700 (PDT) Date: Tue, 11 Jul 2023 09:13:18 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Mark Brown cc: Hugh Dickins , Lorenzo Stoakes , Andrew Morton , Mike Kravetz , Mike Rapoport , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Suren Baghdasaryan , Qi Zheng , Yang Shi , Mel Gorman , Peter Xu , Peter Zijlstra , Will Deacon , Yu Zhao , Alistair Popple , Ralph Campbell , Ira Weiny , Steven Price , SeongJae Park , Huang Ying , Naoya Horiguchi , Christophe Leroy , Zack Rusin , Jason Gunthorpe , Axel Rasmussen , Anshuman Khandual , Pasha Tatashin , Miaohe Lin , Minchan Kim , Christoph Hellwig , Song Liu , Thomas Hellstrom , Ryan Roberts , linux-kernel@vger.kernel.org, linux-mm@kvack.org, regressions@leemhuis.info, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 12/32] mm/vmalloc: vmalloc_to_page() use pte_offset_kernel() In-Reply-To: Message-ID: References: <696386a-84f8-b33c-82e5-f865ed6eb39@google.com> <42279f1f-7b82-40dc-8546-86171018729c@sirena.org.uk> <901ae88d-ad0c-4e9d-b199-f1566cc62a00@lucifer.local> <977ddee4-35f0-fcd1-2fd-1c3057e7ea2a@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 11 Jul 2023, Mark Brown wrote: > On Mon, Jul 10, 2023 at 09:34:42PM -0700, Hugh Dickins wrote: > > > I suppose I should ask you to try reverting this 0d1c81edc61e alone > > from 6.5-rc1: the consistency of your bisection implies that it will > > "fix" the issues, and it is a commit which we could drop. It makes > > me a little nervous, applying userspace-pagetable validation to kernel > > pagetables, so I don't want to drop it; and it would really be cargo- > > culting to drop it without understanding. But we could drop it. > > I did look at that, it doesn't revert cleanly by itself. ... Right, that ptep_get() wrapper on the next line came in on top. The patch to revert just 0d1c81edc61e is this: --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -703,10 +703,11 @@ struct page *vmalloc_to_page(const void if (WARN_ON_ONCE(pmd_bad(*pmd))) return NULL; - ptep = pte_offset_kernel(pmd, addr); + ptep = pte_offset_map(pmd, addr); pte = ptep_get(ptep); if (pte_present(pte)) page = pte_page(pte); + pte_unmap(ptep); return page; }