Page tables in init_pg_dir are always modified via the linear map. kpkeys_hardened_pgtables now prevents arbitrary code from writing page tables via the linear map; map the kernel image alias of init_pg_dir read-only to ensure that the kpkeys protection cannot be bypassed. Reviewed-by: Yeoreum Yun Signed-off-by: Kevin Brodsky --- arch/arm64/include/asm/sections.h | 1 + arch/arm64/kernel/pi/map_kernel.c | 9 +++++++-- arch/arm64/mm/mmu.c | 8 ++++++++ 3 files changed, 16 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/sections.h b/arch/arm64/include/asm/sections.h index 51b0d594239e..dc961cf67168 100644 --- a/arch/arm64/include/asm/sections.h +++ b/arch/arm64/include/asm/sections.h @@ -23,6 +23,7 @@ extern char __irqentry_text_start[], __irqentry_text_end[]; extern char __mmuoff_data_start[], __mmuoff_data_end[]; extern char __entry_tramp_text_start[], __entry_tramp_text_end[]; extern char __relocate_new_kernel_start[], __relocate_new_kernel_end[]; +extern char __pi_init_pg_dir[], __pi_init_pg_end[]; static inline size_t entry_tramp_text_size(void) { diff --git a/arch/arm64/kernel/pi/map_kernel.c b/arch/arm64/kernel/pi/map_kernel.c index fb44cbdd2f29..81ca3e98f0f7 100644 --- a/arch/arm64/kernel/pi/map_kernel.c +++ b/arch/arm64/kernel/pi/map_kernel.c @@ -92,8 +92,13 @@ static void __init map_kernel(u64 kaslr_offset, u64 va_offset, int root_level) __inittext_end, prot, false, root_level); map_segment(init_pg_dir, &pgdp, va_offset, __initdata_begin, __initdata_end, data_prot, false, root_level); - map_segment(init_pg_dir, &pgdp, va_offset, _data, _end, data_prot, - true, root_level); + map_segment(init_pg_dir, &pgdp, va_offset, _data, init_pg_dir, + data_prot, true, root_level); + /* Map init_pg_dir separately as we will remap it read-only later on */ + map_segment(init_pg_dir, &pgdp, va_offset, init_pg_dir, init_pg_end, + data_prot, true, root_level); + map_segment(init_pg_dir, &pgdp, va_offset, init_pg_end, _end, + data_prot, true, root_level); dsb(ishst); idmap_cpu_replace_ttbr1((phys_addr_t)init_pg_dir); diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index c1e3260bd0db..b6a4371dd03f 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -1267,6 +1267,14 @@ void mark_rodata_ro(void) update_mapping_prot(__pa_symbol(_text), (unsigned long)_text, (unsigned long)_stext - (unsigned long)_text, PAGE_KERNEL_RO); + /* + * Map the kernel image mapping of init_pg_dir read-only; it should + * only be written via the linear map. + */ + section_size = (unsigned long)__pi_init_pg_end - (unsigned long)__pi_init_pg_dir; + update_mapping_prot(__pa_symbol(__pi_init_pg_dir), + (unsigned long)__pi_init_pg_dir, + section_size, PAGE_KERNEL_RO); /* Map the kernel data/bss as invalid in the linear map */ mark_linear_data_alias_valid(false); -- 2.56.0