[PATCH v4 15/15] arm64: mm: Remap linear aliases of the fixmap page tables read-only

[Ard Biesheuvel]

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 :-)