From 6fb14755a676282a4e6caa05a08c92db8e45cfff Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Wed, 2 May 2007 19:27:10 +0200 Subject: [PATCH] [PATCH] x86: tighten kernel image page access rights On x86-64, kernel memory freed after init can be entirely unmapped instead of just getting 'poisoned' by overwriting with a debug pattern. On i386 and x86-64 (under CONFIG_DEBUG_RODATA), kernel text and bug table can also be write-protected. Compared to the first version, this one prevents re-creating deleted mappings in the kernel image range on x86-64, if those got removed previously. This, together with the original changes, prevents temporarily having inconsistent mappings when cacheability attributes are being changed on such pages (e.g. from AGP code). While on i386 such duplicate mappings don't exist, the same change is done there, too, both for consistency and because checking pte_present() before using various other pte_XXX functions is a requirement anyway. At once, i386 code gets adjusted to use pte_huge() instead of open coding this. AK: split out cpa() changes Signed-off-by: Jan Beulich Signed-off-by: Andi Kleen --- arch/i386/kernel/vmlinux.lds.S | 4 ++-- arch/i386/mm/init.c | 25 +++++++++++++++++++------ arch/x86_64/kernel/head.S | 1 - arch/x86_64/kernel/vmlinux.lds.S | 5 +++-- arch/x86_64/mm/init.c | 25 ++++++++++++++++--------- include/linux/poison.h | 3 --- 6 files changed, 40 insertions(+), 23 deletions(-) diff --git a/arch/i386/kernel/vmlinux.lds.S b/arch/i386/kernel/vmlinux.lds.S index 6f38f818380b..f4ec72231835 100644 --- a/arch/i386/kernel/vmlinux.lds.S +++ b/arch/i386/kernel/vmlinux.lds.S @@ -61,8 +61,6 @@ SECTIONS __stop___ex_table = .; } - RODATA - BUG_TABLE . = ALIGN(4); @@ -72,6 +70,8 @@ SECTIONS __tracedata_end = .; } + RODATA + /* writeable */ . = ALIGN(4096); .data : AT(ADDR(.data) - LOAD_OFFSET) { /* Data */ diff --git a/arch/i386/mm/init.c b/arch/i386/mm/init.c index 23be1b0aafa4..bd5ef3718504 100644 --- a/arch/i386/mm/init.c +++ b/arch/i386/mm/init.c @@ -22,6 +22,7 @@ #include #include #include +#include #include #include #include @@ -751,13 +752,25 @@ static int noinline do_test_wp_bit(void) void mark_rodata_ro(void) { - unsigned long addr = (unsigned long)__start_rodata; + unsigned long start = PFN_ALIGN(_text); + unsigned long size = PFN_ALIGN(_etext) - start; - for (; addr < (unsigned long)__end_rodata; addr += PAGE_SIZE) - change_page_attr(virt_to_page(addr), 1, PAGE_KERNEL_RO); +#ifdef CONFIG_HOTPLUG_CPU + /* It must still be possible to apply SMP alternatives. */ + if (num_possible_cpus() <= 1) +#endif + { + change_page_attr(virt_to_page(start), + size >> PAGE_SHIFT, PAGE_KERNEL_RX); + printk("Write protecting the kernel text: %luk\n", size >> 10); + } - printk("Write protecting the kernel read-only data: %uk\n", - (__end_rodata - __start_rodata) >> 10); + start += size; + size = (unsigned long)__end_rodata - start; + change_page_attr(virt_to_page(start), + size >> PAGE_SHIFT, PAGE_KERNEL_RO); + printk("Write protecting the kernel read-only data: %luk\n", + size >> 10); /* * change_page_attr() requires a global_flush_tlb() call after it. @@ -781,7 +794,7 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end) __free_page(page); totalram_pages++; } - printk(KERN_INFO "Freeing %s: %ldk freed\n", what, (end - begin) >> 10); + printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10); } void free_initmem(void) diff --git a/arch/x86_64/kernel/head.S b/arch/x86_64/kernel/head.S index 36aa98a6d15c..fd9fdfdd143e 100644 --- a/arch/x86_64/kernel/head.S +++ b/arch/x86_64/kernel/head.S @@ -280,7 +280,6 @@ early_idt_ripmsg: .balign PAGE_SIZE ENTRY(stext) -ENTRY(_stext) #define NEXT_PAGE(name) \ .balign PAGE_SIZE; \ diff --git a/arch/x86_64/kernel/vmlinux.lds.S b/arch/x86_64/kernel/vmlinux.lds.S index 5176ecf006ee..3bdeb88d28f4 100644 --- a/arch/x86_64/kernel/vmlinux.lds.S +++ b/arch/x86_64/kernel/vmlinux.lds.S @@ -29,6 +29,7 @@ SECTIONS .text : AT(ADDR(.text) - LOAD_OFFSET) { /* First the code that has to be first for bootstrapping */ *(.bootstrap.text) + _stext = .; /* Then all the functions that are "hot" in profiles, to group them onto the same hugetlb entry */ #include "functionlist" @@ -50,10 +51,10 @@ SECTIONS __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { *(__ex_table) } __stop___ex_table = .; - RODATA - BUG_TABLE + RODATA + . = ALIGN(PAGE_SIZE); /* Align data segment to page size boundary */ /* Data */ .data : AT(ADDR(.data) - LOAD_OFFSET) { diff --git a/arch/x86_64/mm/init.c b/arch/x86_64/mm/init.c index 69e22d3c9238..e3134bc9a4fc 100644 --- a/arch/x86_64/mm/init.c +++ b/arch/x86_64/mm/init.c @@ -22,6 +22,7 @@ #include #include #include +#include #include #include #include @@ -563,21 +564,23 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end) if (begin >= end) return; - printk(KERN_INFO "Freeing %s: %ldk freed\n", what, (end - begin) >> 10); + printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10); for (addr = begin; addr < end; addr += PAGE_SIZE) { struct page *page = pfn_to_page(addr >> PAGE_SHIFT); ClearPageReserved(page); init_page_count(page); memset(page_address(page), POISON_FREE_INITMEM, PAGE_SIZE); + if (addr >= __START_KERNEL_map) + change_page_attr_addr(addr, 1, __pgprot(0)); __free_page(page); totalram_pages++; } + if (addr > __START_KERNEL_map) + global_flush_tlb(); } void free_initmem(void) { - memset(__initdata_begin, POISON_FREE_INITDATA, - __initdata_end - __initdata_begin); free_init_pages("unused kernel memory", __pa_symbol(&__init_begin), __pa_symbol(&__init_end)); @@ -587,14 +590,18 @@ void free_initmem(void) void mark_rodata_ro(void) { - unsigned long addr = (unsigned long)__va(__pa_symbol(&__start_rodata)); - unsigned long end = (unsigned long)__va(__pa_symbol(&__end_rodata)); + unsigned long start = PFN_ALIGN(__va(__pa_symbol(&_stext))), size; - for (; addr < end; addr += PAGE_SIZE) - change_page_attr_addr(addr, 1, PAGE_KERNEL_RO); +#ifdef CONFIG_HOTPLUG_CPU + /* It must still be possible to apply SMP alternatives. */ + if (num_possible_cpus() > 1) + start = PFN_ALIGN(__va(__pa_symbol(&_etext))); +#endif + size = (unsigned long)__va(__pa_symbol(&__end_rodata)) - start; + change_page_attr_addr(start, size >> PAGE_SHIFT, PAGE_KERNEL_RO); - printk ("Write protecting the kernel read-only data: %luk\n", - (__end_rodata - __start_rodata) >> 10); + printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n", + size >> 10); /* * change_page_attr_addr() requires a global_flush_tlb() call after it. diff --git a/include/linux/poison.h b/include/linux/poison.h index 3e628f990fdf..89580b764959 100644 --- a/include/linux/poison.h +++ b/include/linux/poison.h @@ -26,9 +26,6 @@ /********** arch/$ARCH/mm/init.c **********/ #define POISON_FREE_INITMEM 0xcc -/********** arch/x86_64/mm/init.c **********/ -#define POISON_FREE_INITDATA 0xba - /********** arch/ia64/hp/common/sba_iommu.c **********/ /* * arch/ia64/hp/common/sba_iommu.c uses a 16-byte poison string with a -- 2.20.1