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Wed, 29 Apr 2026 10:09:08 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Wed, 29 Apr 2026 16:08:48 +0200 From: "Ard Biesheuvel" To: "Kevin Brodsky" , "Ard Biesheuvel" , linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, "Will Deacon" , "Catalin Marinas" , "Mark Rutland" , "Ryan Roberts" , "Anshuman Khandual" , "Liz Prucka" , "Seth Jenkins" , "Kees Cook" , "Mike Rapoport" , "David Hildenbrand" , "Andrew Morton" , linux-mm@kvack.org, linux-hardening@vger.kernel.org Message-Id: <5e0a87ad-50d5-420b-ad5a-c2882a619b35@app.fastmail.com> In-Reply-To: <21a547ae-7121-4cd1-b203-4d8182eb7cc9@arm.com> References: <20260427153416.2103979-17-ardb+git@google.com> <20260427153416.2103979-32-ardb+git@google.com> <21a547ae-7121-4cd1-b203-4d8182eb7cc9@arm.com> Subject: Re: [PATCH v4 15/15] arm64: mm: Remap linear aliases of the fixmap page tables read-only Content-Type: text/plain Content-Transfer-Encoding: 7bit Hi Ard, On Wed, 29 Apr 2026, at 15:57, Kevin Brodsky wrote: > On 27/04/2026 17:34, Ard Biesheuvel wrote: >> [...] >> >> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >> index 84d81bae07a7..e76fe5b0c5fe 100644 >> --- a/arch/arm64/mm/mmu.c >> +++ b/arch/arm64/mm/mmu.c >> @@ -1076,6 +1076,11 @@ void __init mark_linear_text_alias_ro(void) >> (unsigned long)__init_begin - (unsigned long)_text, >> pgprot_tagged(PAGE_KERNEL_RO)); >> >> + /* Map the fixmap PTE table at __fixmap_pgdir_start R/O in linear map too */ >> + update_mapping_prot(__pa_symbol(__fixmap_pgdir_start), >> + (unsigned long)lm_alias(__fixmap_pgdir_start), >> + PAGE_SIZE, pgprot_tagged(PAGE_KERNEL_RO)); > > Is that definitely just one page? > No it most definitely is not - thanks for spotting that :-)