From f47233c2d34f243ecdaac179c3408a39ff9216a7 Mon Sep 17 00:00:00 2001 From: Jiri Kosina Date: Fri, 13 Feb 2015 16:04:55 +0100 Subject: x86/mm/ASLR: Propagate base load address calculation Commit: e2b32e678513 ("x86, kaslr: randomize module base load address") makes the base address for module to be unconditionally randomized in case when CONFIG_RANDOMIZE_BASE is defined and "nokaslr" option isn't present on the commandline. This is not consistent with how choose_kernel_location() decides whether it will randomize kernel load base. Namely, CONFIG_HIBERNATION disables kASLR (unless "kaslr" option is explicitly specified on kernel commandline), which makes the state space larger than what module loader is looking at. IOW CONFIG_HIBERNATION && CONFIG_RANDOMIZE_BASE is a valid config option, kASLR wouldn't be applied by default in that case, but module loader is not aware of that. Instead of fixing the logic in module.c, this patch takes more generic aproach. It introduces a new bootparam setup data_type SETUP_KASLR and uses that to pass the information whether kaslr has been applied during kernel decompression, and sets a global 'kaslr_enabled' variable accordingly, so that any kernel code (module loading, livepatching, ...) can make decisions based on its value. x86 module loader is converted to make use of this flag. Signed-off-by: Jiri Kosina Acked-by: Kees Cook Cc: "H. Peter Anvin" Link: https://lkml.kernel.org/r/alpine.LNX.2.00.1502101411280.10719@pobox.suse.cz [ Always dump correct kaslr status when panicking ] Signed-off-by: Borislav Petkov diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c index bb13763..7083c16 100644 --- a/arch/x86/boot/compressed/aslr.c +++ b/arch/x86/boot/compressed/aslr.c @@ -14,6 +14,13 @@ static const char build_str[] = UTS_RELEASE " (" LINUX_COMPILE_BY "@" LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION; +struct kaslr_setup_data { + __u64 next; + __u32 type; + __u32 len; + __u8 data[1]; +} kaslr_setup_data; + #define I8254_PORT_CONTROL 0x43 #define I8254_PORT_COUNTER0 0x40 #define I8254_CMD_READBACK 0xC0 @@ -295,7 +302,29 @@ static unsigned long find_random_addr(unsigned long minimum, return slots_fetch_random(); } -unsigned char *choose_kernel_location(unsigned char *input, +static void add_kaslr_setup_data(struct boot_params *params, __u8 enabled) +{ + struct setup_data *data; + + kaslr_setup_data.type = SETUP_KASLR; + kaslr_setup_data.len = 1; + kaslr_setup_data.next = 0; + kaslr_setup_data.data[0] = enabled; + + data = (struct setup_data *)(unsigned long)params->hdr.setup_data; + + while (data && data->next) + data = (struct setup_data *)(unsigned long)data->next; + + if (data) + data->next = (unsigned long)&kaslr_setup_data; + else + params->hdr.setup_data = (unsigned long)&kaslr_setup_data; + +} + +unsigned char *choose_kernel_location(struct boot_params *params, + unsigned char *input, unsigned long input_size, unsigned char *output, unsigned long output_size) @@ -306,14 +335,17 @@ unsigned char *choose_kernel_location(unsigned char *input, #ifdef CONFIG_HIBERNATION if (!cmdline_find_option_bool("kaslr")) { debug_putstr("KASLR disabled by default...\n"); + add_kaslr_setup_data(params, 0); goto out; } #else if (cmdline_find_option_bool("nokaslr")) { debug_putstr("KASLR disabled by cmdline...\n"); + add_kaslr_setup_data(params, 0); goto out; } #endif + add_kaslr_setup_data(params, 1); /* Record the various known unsafe memory ranges. */ mem_avoid_init((unsigned long)input, input_size, diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index a950864..5903089 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -401,7 +401,8 @@ asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap, * the entire decompressed kernel plus relocation table, or the * entire decompressed kernel plus .bss and .brk sections. */ - output = choose_kernel_location(input_data, input_len, output, + output = choose_kernel_location(real_mode, input_data, input_len, + output, output_len > run_size ? output_len : run_size); diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h index 24e3e56..6d67307 100644 --- a/arch/x86/boot/compressed/misc.h +++ b/arch/x86/boot/compressed/misc.h @@ -56,7 +56,8 @@ int cmdline_find_option_bool(const char *option); #if CONFIG_RANDOMIZE_BASE /* aslr.c */ -unsigned char *choose_kernel_location(unsigned char *input, +unsigned char *choose_kernel_location(struct boot_params *params, + unsigned char *input, unsigned long input_size, unsigned char *output, unsigned long output_size); @@ -64,7 +65,8 @@ unsigned char *choose_kernel_location(unsigned char *input, bool has_cpuflag(int flag); #else static inline -unsigned char *choose_kernel_location(unsigned char *input, +unsigned char *choose_kernel_location(struct boot_params *params, + unsigned char *input, unsigned long input_size, unsigned char *output, unsigned long output_size) diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h index f97fbe3..3d43ce3 100644 --- a/arch/x86/include/asm/page_types.h +++ b/arch/x86/include/asm/page_types.h @@ -3,6 +3,7 @@ #include #include +#include /* PAGE_SHIFT determines the page size */ #define PAGE_SHIFT 12 @@ -51,6 +52,8 @@ extern int devmem_is_allowed(unsigned long pagenr); extern unsigned long max_low_pfn_mapped; extern unsigned long max_pfn_mapped; +extern bool kaslr_enabled; + static inline phys_addr_t get_max_mapped(void) { return (phys_addr_t)max_pfn_mapped << PAGE_SHIFT; diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h index 225b098..44e6dd7 100644 --- a/arch/x86/include/uapi/asm/bootparam.h +++ b/arch/x86/include/uapi/asm/bootparam.h @@ -7,6 +7,7 @@ #define SETUP_DTB 2 #define SETUP_PCI 3 #define SETUP_EFI 4 +#define SETUP_KASLR 5 /* ram_size flags */ #define RAMDISK_IMAGE_START_MASK 0x07FF diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c index e69f988..c3c59a3 100644 --- a/arch/x86/kernel/module.c +++ b/arch/x86/kernel/module.c @@ -32,6 +32,7 @@ #include #include +#include #if 0 #define DEBUGP(fmt, ...) \ @@ -46,21 +47,13 @@ do { \ #ifdef CONFIG_RANDOMIZE_BASE static unsigned long module_load_offset; -static int randomize_modules = 1; /* Mutex protects the module_load_offset. */ static DEFINE_MUTEX(module_kaslr_mutex); -static int __init parse_nokaslr(char *p) -{ - randomize_modules = 0; - return 0; -} -early_param("nokaslr", parse_nokaslr); - static unsigned long int get_module_load_offset(void) { - if (randomize_modules) { + if (kaslr_enabled) { mutex_lock(&module_kaslr_mutex); /* * Calculate the module_load_offset the first time this diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index ab4734e..16b6043 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -121,6 +121,8 @@ unsigned long max_low_pfn_mapped; unsigned long max_pfn_mapped; +bool __read_mostly kaslr_enabled = false; + #ifdef CONFIG_DMI RESERVE_BRK(dmi_alloc, 65536); #endif @@ -424,6 +426,11 @@ static void __init reserve_initrd(void) } #endif /* CONFIG_BLK_DEV_INITRD */ +static void __init parse_kaslr_setup(u64 pa_data, u32 data_len) +{ + kaslr_enabled = (bool)(pa_data + sizeof(struct setup_data)); +} + static void __init parse_setup_data(void) { struct setup_data *data; @@ -451,6 +458,9 @@ static void __init parse_setup_data(void) case SETUP_EFI: parse_efi_setup(pa_data, data_len); break; + case SETUP_KASLR: + parse_kaslr_setup(pa_data, data_len); + break; default: break; } @@ -833,10 +843,14 @@ static void __init trim_low_memory_range(void) static int dump_kernel_offset(struct notifier_block *self, unsigned long v, void *p) { - pr_emerg("Kernel Offset: 0x%lx from 0x%lx " - "(relocation range: 0x%lx-0x%lx)\n", - (unsigned long)&_text - __START_KERNEL, __START_KERNEL, - __START_KERNEL_map, MODULES_VADDR-1); + if (kaslr_enabled) + pr_emerg("Kernel Offset: 0x%lx from 0x%lx (relocation range: 0x%lx-0x%lx)\n", + (unsigned long)&_text - __START_KERNEL, + __START_KERNEL, + __START_KERNEL_map, + MODULES_VADDR-1); + else + pr_emerg("Kernel Offset: disabled\n"); return 0; } -- cgit v0.10.2 From 4e7c22d447bb6d7e37bfe39ff658486ae78e8d77 Mon Sep 17 00:00:00 2001 From: Hector Marco-Gisbert Date: Sat, 14 Feb 2015 09:33:50 -0800 Subject: x86, mm/ASLR: Fix stack randomization on 64-bit systems The issue is that the stack for processes is not properly randomized on 64 bit architectures due to an integer overflow. The affected function is randomize_stack_top() in file "fs/binfmt_elf.c": static unsigned long randomize_stack_top(unsigned long stack_top) { unsigned int random_variable = 0; if ((current->flags & PF_RANDOMIZE) && !(current->personality & ADDR_NO_RANDOMIZE)) { random_variable = get_random_int() & STACK_RND_MASK; random_variable <<= PAGE_SHIFT; } return PAGE_ALIGN(stack_top) + random_variable; return PAGE_ALIGN(stack_top) - random_variable; } Note that, it declares the "random_variable" variable as "unsigned int". Since the result of the shifting operation between STACK_RND_MASK (which is 0x3fffff on x86_64, 22 bits) and PAGE_SHIFT (which is 12 on x86_64): random_variable <<= PAGE_SHIFT; then the two leftmost bits are dropped when storing the result in the "random_variable". This variable shall be at least 34 bits long to hold the (22+12) result. These two dropped bits have an impact on the entropy of process stack. Concretely, the total stack entropy is reduced by four: from 2^28 to 2^30 (One fourth of expected entropy). This patch restores back the entropy by correcting the types involved in the operations in the functions randomize_stack_top() and stack_maxrandom_size(). The successful fix can be tested with: $ for i in `seq 1 10`; do cat /proc/self/maps | grep stack; done 7ffeda566000-7ffeda587000 rw-p 00000000 00:00 0 [stack] 7fff5a332000-7fff5a353000 rw-p 00000000 00:00 0 [stack] 7ffcdb7a1000-7ffcdb7c2000 rw-p 00000000 00:00 0 [stack] 7ffd5e2c4000-7ffd5e2e5000 rw-p 00000000 00:00 0 [stack] ... Once corrected, the leading bytes should be between 7ffc and 7fff, rather than always being 7fff. Signed-off-by: Hector Marco-Gisbert Signed-off-by: Ismael Ripoll [ Rebased, fixed 80 char bugs, cleaned up commit message, added test example and CVE ] Signed-off-by: Kees Cook Cc: Cc: Linus Torvalds Cc: Andrew Morton Cc: Al Viro Fixes: CVE-2015-1593 Link: http://lkml.kernel.org/r/20150214173350.GA18393@www.outflux.net Signed-off-by: Borislav Petkov diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index 919b912..df4552b 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -35,12 +35,12 @@ struct va_alignment __read_mostly va_align = { .flags = -1, }; -static unsigned int stack_maxrandom_size(void) +static unsigned long stack_maxrandom_size(void) { - unsigned int max = 0; + unsigned long max = 0; if ((current->flags & PF_RANDOMIZE) && !(current->personality & ADDR_NO_RANDOMIZE)) { - max = ((-1U) & STACK_RND_MASK) << PAGE_SHIFT; + max = ((-1UL) & STACK_RND_MASK) << PAGE_SHIFT; } return max; diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 02b1691..995986b 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -645,11 +645,12 @@ out: static unsigned long randomize_stack_top(unsigned long stack_top) { - unsigned int random_variable = 0; + unsigned long random_variable = 0; if ((current->flags & PF_RANDOMIZE) && !(current->personality & ADDR_NO_RANDOMIZE)) { - random_variable = get_random_int() & STACK_RND_MASK; + random_variable = (unsigned long) get_random_int(); + random_variable &= STACK_RND_MASK; random_variable <<= PAGE_SHIFT; } #ifdef CONFIG_STACK_GROWSUP -- cgit v0.10.2