From f15e05186c3244e9195378a0a568283a8ccc60b0 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Tue, 10 Feb 2015 13:20:30 -0800 Subject: x86/mm/init: Fix incorrect page size in init_memory_mapping() printks With 32-bit non-PAE kernels, we have 2 page sizes available (at most): 4k and 4M. Enabling PAE replaces that 4M size with a 2M one (which 64-bit systems use too). But, when booting a 32-bit non-PAE kernel, in one of our early-boot printouts, we say: init_memory_mapping: [mem 0x00000000-0x000fffff] [mem 0x00000000-0x000fffff] page 4k init_memory_mapping: [mem 0x37000000-0x373fffff] [mem 0x37000000-0x373fffff] page 2M init_memory_mapping: [mem 0x00100000-0x36ffffff] [mem 0x00100000-0x003fffff] page 4k [mem 0x00400000-0x36ffffff] page 2M init_memory_mapping: [mem 0x37400000-0x377fdfff] [mem 0x37400000-0x377fdfff] page 4k Which is obviously wrong. There is no 2M page available. This is probably because of a badly-named variable: in the map_range code: PG_LEVEL_2M. Instead of renaming all the PG_LEVEL_2M's. This patch just fixes the printout: init_memory_mapping: [mem 0x00000000-0x000fffff] [mem 0x00000000-0x000fffff] page 4k init_memory_mapping: [mem 0x37000000-0x373fffff] [mem 0x37000000-0x373fffff] page 4M init_memory_mapping: [mem 0x00100000-0x36ffffff] [mem 0x00100000-0x003fffff] page 4k [mem 0x00400000-0x36ffffff] page 4M init_memory_mapping: [mem 0x37400000-0x377fdfff] [mem 0x37400000-0x377fdfff] page 4k BRK [0x03206000, 0x03206fff] PGTABLE Signed-off-by: Dave Hansen Cc: Pekka Enberg Cc: Yinghai Lu Link: http://lkml.kernel.org/r/20150210212030.665EC267@viggo.jf.intel.com Signed-off-by: Borislav Petkov --- arch/x86/mm/init.c | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-) (limited to 'arch/x86/mm') diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index 079c3b6..7ff2424 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -238,6 +238,31 @@ static void __init_refok adjust_range_page_size_mask(struct map_range *mr, } } +static const char *page_size_string(struct map_range *mr) +{ + static const char str_1g[] = "1G"; + static const char str_2m[] = "2M"; + static const char str_4m[] = "4M"; + static const char str_4k[] = "4k"; + + if (mr->page_size_mask & (1<page_size_mask & (1<page_size_mask & (1< 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 --- arch/x86/mm/mmap.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'arch/x86/mm') 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; -- cgit v1.1