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b=eNPPFp5qbKoJvjUdtGg8w3IZMg0vNZv6+vkTJLLSWou52vAtg3PDH+YXoVUKkouG2 Tp5I1zPHI6skDu0RSAecz1Q5bIQEjW4D5u6sgFWBLlB3ZBkSkoh5xEUlGn3n1eSJGK peEKGToSl+aX/tl3OJYA18f9PnOfG4kNUughduRc= Date: Sun, 5 Jul 2026 01:33:37 -0700 From: Andrew Morton To: Dev Jain Cc: muchun.song@linux.dev, osalvador@suse.de, ljs@kernel.org, david@kernel.org, liam@infradead.org, riel@surriel.com, vbabka@kernel.org, harry@kernel.org, jannh@google.com, lance.yang@linux.dev, kas@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, apopple@nvidia.com, rcampbell@nvidia.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, ak@linux.intel.com, nao.horiguchi@gmail.com, mel@csn.ul.ie, j-nomura@ce.jp.nec.com, pfalcato@suse.de, tglx@kernel.org, dave.hansen@intel.com, jpoimboe@kernel.org, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, ryan.roberts@arm.com, anshuman.khandual@arm.com Subject: Re: [PATCH v3 6/6] mm/mprotect: use huge_ptep_get() for hugetlb Message-Id: <20260705013337.2bbc075b508b5db36b954051@linux-foundation.org> In-Reply-To: <20260703114202.365553-7-dev.jain@arm.com> References: <20260703114202.365553-1-dev.jain@arm.com> <20260703114202.365553-7-dev.jain@arm.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: BFAD740007 X-Stat-Signature: j74h1nwjpjgnthaupoxsjw5ues15w63q X-HE-Tag: 1783240419-960344 X-HE-Meta: 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 dgMrysQg ncM26viiZmjYiLd/XuipOLNKTvmwcaToZjTNzoHJzZOT9pvHgMr0rS9Xcer7zwLyaCGuEcM7J4MmtRzaKgVMGVXfnCSrbcvHak/Fl5vvl9J9nkxalozERxOs0x8spk/zrdTZLftG70r5Vb7bUXPgekFqgTJ60lTWn4Zdncmq8HaTXklOJL1l1v2NatQRyMiYP0l85Hwjztg+UfwAKU0rw826q8H8yS1cGgSyaJv9YsIk12uXWPOF1WnNUwhV6kBAAFE6gMaRbHQRNcvB/va0zhnq1ibwcp8halJAXYTZfyPaLmAWG9i6vCpOBf3cF0jRw6cNk4FLAJtAIwX7A7dEhzmqmnLNukg3GTIXyRKCRcwdssvRNmU+Y80512Fw6uNnJ3ujcf5hK3Cgdqi++/I2MkZGR+uGl+1agTrpeDH3wnDi+NbOfzHlsIbCMcw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 3 Jul 2026 11:41:59 +0000 Dev Jain wrote: > prot_none_hugetlb_entry() is the hugetlb callback for the early > mprotect(PROT_NONE) PFN permission walk on x86. > > The callback passes the decoded PFN to pfn_modify_allowed(). For a > hugetlb callback, the pte pointer refers to a hugetlb entry. On > architectures where hugetlb entries need huge_ptep_get(), reading that > entry with ptep_get() can make the permission check use the wrong PFN. > > Use huge_ptep_get() before decoding the hugetlb PFN. > > Currently there is no path which can trigger a bug: huge_ptep_get() is a > simple ptep_get() for x86, and the prot_none walk occurs only for x86. > > So no need to backport - use the correct helper anyways. > > ... > > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -699,14 +699,20 @@ static int prot_none_pte_entry(pte_t *pte, unsigned long addr, > 0 : -EACCES; > } > > +#ifdef CONFIG_HUGETLB_PAGE > static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask, > unsigned long addr, unsigned long next, > struct mm_walk *walk) > { > - return pfn_modify_allowed(pte_pfn(ptep_get(pte)), > - *(pgprot_t *)(walk->private)) ? > - 0 : -EACCES; > + const pte_t entry = huge_ptep_get(walk->mm, addr, pte); > + > + if (pfn_modify_allowed(pte_pfn(entry), *(pgprot_t *)(walk->private))) > + return 0; > + return -EACCESS; "EACCES". > } > +#else > +#define prot_none_hugetlb_entry NULL > +#endif Presumably your .config resulted in this change not being tested...