Messages in this thread | | | Date | Thu, 22 Sep 2022 08:21:38 +0530 | Subject | Re: [PATCH] arm64/mm: fold check for KFENCE into can_set_direct_map() | From | Anshuman Khandual <> |
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On 9/21/22 20:49, Mike Rapoport wrote: > Hi Anshuman, > > On Wed, Sep 21, 2022 at 05:09:19PM +0530, Anshuman Khandual wrote: >> >> >> On 9/21/22 13:18, Mike Rapoport wrote: >>> From: Mike Rapoport <rppt@linux.ibm.com> >>> >>> KFENCE requires linear map to be mapped at page granularity, so that it >>> is possible to protect/unprotect single pages, just like with >>> rodata_full and DEBUG_PAGEALLOC. >>> >>> Instead of repating >>> >>> can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE) >>> >>> make can_set_direct_map() handle the KFENCE case. >>> >>> This also prevents potential false positives in kernel_page_present() >>> that may return true for non-present page if CONFIG_KFENCE is enabled. >>> >>> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com> >>> --- >>> arch/arm64/mm/mmu.c | 8 ++------ >>> arch/arm64/mm/pageattr.c | 8 +++++++- >>> 2 files changed, 9 insertions(+), 7 deletions(-) >>> >>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >>> index e7ad44585f40..c5065abec55a 100644 >>> --- a/arch/arm64/mm/mmu.c >>> +++ b/arch/arm64/mm/mmu.c >>> @@ -535,7 +535,7 @@ static void __init map_mem(pgd_t *pgdp) >>> */ >>> BUILD_BUG_ON(pgd_index(direct_map_end - 1) == pgd_index(direct_map_end)); >>> >>> - if (can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE)) >>> + if (can_set_direct_map()) >>> flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; >>> >>> /* >>> @@ -1547,11 +1547,7 @@ int arch_add_memory(int nid, u64 start, u64 size, >>> >>> VM_BUG_ON(!mhp_range_allowed(start, size, true)); >>> >>> - /* >>> - * KFENCE requires linear map to be mapped at page granularity, so that >>> - * it is possible to protect/unprotect single pages in the KFENCE pool. >>> - */ >>> - if (can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE)) >>> + if (can_set_direct_map()) >>> flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; >>> >>> __create_pgd_mapping(swapper_pg_dir, start, __phys_to_virt(start), >>> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c >>> index 64e985eaa52d..d107c3d434e2 100644 >>> --- a/arch/arm64/mm/pageattr.c >>> +++ b/arch/arm64/mm/pageattr.c >>> @@ -21,7 +21,13 @@ bool rodata_full __ro_after_init = IS_ENABLED(CONFIG_RODATA_FULL_DEFAULT_ENABLED >>> >>> bool can_set_direct_map(void) >>> { >>> - return rodata_full || debug_pagealloc_enabled(); >>> + /* >>> + * rodata_full, DEBUG_PAGEALLOC and KFENCE require linear map to be >>> + * mapped at page granularity, so that it is possible to >>> + * protect/unprotect single pages. >>> + */ >>> + return rodata_full || debug_pagealloc_enabled() || >>> + IS_ENABLED(CONFIG_KFENCE); >>> } >> >> Changing can_set_direct_map() also changes behaviour for other functions such as >> >> set_direct_map_default_noflush() >> set_direct_map_invalid_noflush() >> __kernel_map_pages() >> >> Is that okay ? > > Yes. Since KFENCE disables block mappings, these will actually change the > page tables. > Actually, before this change the test for can_set_direct_map() in these > functions was false negative when CONFIG_KFENCE=y
Okay but then should not this have a "Fixes:" tag as well ?
> >>> static int change_page_range(pte_t *ptep, unsigned long addr, void *data) >
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