diff options
Diffstat (limited to 'arch/arm/mm')
| -rw-r--r-- | arch/arm/mm/Kconfig | 34 | ||||
| -rw-r--r-- | arch/arm/mm/init.c | 19 |
2 files changed, 28 insertions, 25 deletions
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig index 549f6d3aec5b..4daeda0a5b7f 100644 --- a/arch/arm/mm/Kconfig +++ b/arch/arm/mm/Kconfig @@ -1037,24 +1037,26 @@ config ARCH_SUPPORTS_BIG_ENDIAN This option specifies the architecture can support big endian operation. -config ARM_KERNMEM_PERMS - bool "Restrict kernel memory permissions" +config DEBUG_RODATA + bool "Make kernel text and rodata read-only" depends on MMU + default y if CPU_V7 help - If this is set, kernel memory other than kernel text (and rodata) - will be made non-executable. The tradeoff is that each region is - padded to section-size (1MiB) boundaries (because their permissions - are different and splitting the 1M pages into 4K ones causes TLB - performance problems), wasting memory. + If this is set, kernel text and rodata memory will be made + read-only, and non-text kernel memory will be made non-executable. + The tradeoff is that each region is padded to section-size (1MiB) + boundaries (because their permissions are different and splitting + the 1M pages into 4K ones causes TLB performance problems), which + can waste memory. -config DEBUG_RODATA - bool "Make kernel text and rodata read-only" - depends on ARM_KERNMEM_PERMS +config DEBUG_ALIGN_RODATA + bool "Make rodata strictly non-executable" + depends on DEBUG_RODATA default y help - If this is set, kernel text and rodata will be made read-only. This - is to help catch accidental or malicious attempts to change the - kernel's executable code. Additionally splits rodata from kernel - text so it can be made explicitly non-executable. This creates - another section-size padded region, so it can waste more memory - space while gaining the read-only protections. + If this is set, rodata will be made explicitly non-executable. This + provides protection on the rare chance that attackers might find and + use ROP gadgets that exist in the rodata section. This adds an + additional section-aligned split of rodata from kernel text so it + can be made explicitly non-executable. This padding may waste memory + space to gain the additional protection. diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c index 49bd08178008..53f42508025b 100644 --- a/arch/arm/mm/init.c +++ b/arch/arm/mm/init.c @@ -572,8 +572,9 @@ void __init mem_init(void) } } -#ifdef CONFIG_ARM_KERNMEM_PERMS +#ifdef CONFIG_DEBUG_RODATA struct section_perm { + const char *name; unsigned long start; unsigned long end; pmdval_t mask; @@ -584,6 +585,7 @@ struct section_perm { static struct section_perm nx_perms[] = { /* Make pages tables, etc before _stext RW (set NX). */ { + .name = "pre-text NX", .start = PAGE_OFFSET, .end = (unsigned long)_stext, .mask = ~PMD_SECT_XN, @@ -591,14 +593,16 @@ static struct section_perm nx_perms[] = { }, /* Make init RW (set NX). */ { + .name = "init NX", .start = (unsigned long)__init_begin, .end = (unsigned long)_sdata, .mask = ~PMD_SECT_XN, .prot = PMD_SECT_XN, }, -#ifdef CONFIG_DEBUG_RODATA +#ifdef CONFIG_DEBUG_ALIGN_RODATA /* Make rodata NX (set RO in ro_perms below). */ { + .name = "rodata NX", .start = (unsigned long)__start_rodata, .end = (unsigned long)__init_begin, .mask = ~PMD_SECT_XN, @@ -607,10 +611,10 @@ static struct section_perm nx_perms[] = { #endif }; -#ifdef CONFIG_DEBUG_RODATA static struct section_perm ro_perms[] = { /* Make kernel code and rodata RX (set RO). */ { + .name = "text/rodata RO", .start = (unsigned long)_stext, .end = (unsigned long)__init_begin, #ifdef CONFIG_ARM_LPAE @@ -623,7 +627,6 @@ static struct section_perm ro_perms[] = { #endif }, }; -#endif /* * Updates section permissions only for the current mm (sections are @@ -670,8 +673,8 @@ void set_section_perms(struct section_perm *perms, int n, bool set, for (i = 0; i < n; i++) { if (!IS_ALIGNED(perms[i].start, SECTION_SIZE) || !IS_ALIGNED(perms[i].end, SECTION_SIZE)) { - pr_err("BUG: section %lx-%lx not aligned to %lx\n", - perms[i].start, perms[i].end, + pr_err("BUG: %s section %lx-%lx not aligned to %lx\n", + perms[i].name, perms[i].start, perms[i].end, SECTION_SIZE); continue; } @@ -712,7 +715,6 @@ void fix_kernmem_perms(void) stop_machine(__fix_kernmem_perms, NULL, NULL); } -#ifdef CONFIG_DEBUG_RODATA int __mark_rodata_ro(void *unused) { update_sections_early(ro_perms, ARRAY_SIZE(ro_perms)); @@ -735,11 +737,10 @@ void set_kernel_text_ro(void) set_section_perms(ro_perms, ARRAY_SIZE(ro_perms), true, current->active_mm); } -#endif /* CONFIG_DEBUG_RODATA */ #else static inline void fix_kernmem_perms(void) { } -#endif /* CONFIG_ARM_KERNMEM_PERMS */ +#endif /* CONFIG_DEBUG_RODATA */ void free_tcmmem(void) { |