From dcc94e7ac7e360baae35685257d55c51142abfd9 Mon Sep 17 00:00:00 2001 From: dcashman Date: Tue, 29 Dec 2015 14:24:39 -0800 Subject: [PATCH] FROMLIST: mm: mmap: Add new /proc tunable for mmap_base ASLR. (cherry picked from commit https://lkml.org/lkml/2015/12/21/337) ASLR only uses as few as 8 bits to generate the random offset for the mmap base address on 32 bit architectures. This value was chosen to prevent a poorly chosen value from dividing the address space in such a way as to prevent large allocations. This may not be an issue on all platforms. Allow the specification of a minimum number of bits so that platforms desiring greater ASLR protection may determine where to place the trade-off. Bug: 24047224 Signed-off-by: Daniel Cashman Signed-off-by: Daniel Cashman Change-Id: Ic74424e07710cd9ccb4a02871a829d14ef0cc4bc --- Documentation/sysctl/vm.txt | 29 ++++++++++++++++ arch/Kconfig | 68 +++++++++++++++++++++++++++++++++++++ include/linux/mm.h | 11 ++++++ kernel/sysctl.c | 22 ++++++++++++ mm/mmap.c | 12 +++++++ 5 files changed, 142 insertions(+) diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt index 96f0ee825bed..5f96262a09a4 100644 --- a/Documentation/sysctl/vm.txt +++ b/Documentation/sysctl/vm.txt @@ -40,6 +40,8 @@ Currently, these files are in /proc/sys/vm: - min_slab_ratio - min_unmapped_ratio - mmap_min_addr +- mmap_rnd_bits +- mmap_rnd_compat_bits - nr_hugepages - nr_overcommit_hugepages - nr_pdflush_threads @@ -409,6 +411,33 @@ against future potential kernel bugs. ============================================================== +mmap_rnd_bits: + +This value can be used to select the number of bits to use to +determine the random offset to the base address of vma regions +resulting from mmap allocations on architectures which support +tuning address space randomization. This value will be bounded +by the architecture's minimum and maximum supported values. + +This value can be changed after boot using the +/proc/sys/vm/mmap_rnd_bits tunable + +============================================================== + +mmap_rnd_compat_bits: + +This value can be used to select the number of bits to use to +determine the random offset to the base address of vma regions +resulting from mmap allocations for applications run in +compatibility mode on architectures which support tuning address +space randomization. This value will be bounded by the +architecture's minimum and maximum supported values. + +This value can be changed after boot using the +/proc/sys/vm/mmap_rnd_compat_bits tunable + +============================================================== + nr_hugepages Change the minimum size of the hugepage pool. diff --git a/arch/Kconfig b/arch/Kconfig index 01419d3ee979..5c0b6e359f20 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -253,4 +253,72 @@ config SECCOMP_FILTER See Documentation/prctl/seccomp_filter.txt for details. +config HAVE_ARCH_MMAP_RND_BITS + bool + help + An arch should select this symbol if it supports setting a variable + number of bits for use in establishing the base address for mmap + allocations, has MMU enabled and provides values for both: + - ARCH_MMAP_RND_BITS_MIN + - ARCH_MMAP_RND_BITS_MAX + +config ARCH_MMAP_RND_BITS_MIN + int + +config ARCH_MMAP_RND_BITS_MAX + int + +config ARCH_MMAP_RND_BITS_DEFAULT + int + +config ARCH_MMAP_RND_BITS + int "Number of bits to use for ASLR of mmap base address" if EXPERT + range ARCH_MMAP_RND_BITS_MIN ARCH_MMAP_RND_BITS_MAX + default ARCH_MMAP_RND_BITS_DEFAULT if ARCH_MMAP_RND_BITS_DEFAULT + default ARCH_MMAP_RND_BITS_MIN + depends on HAVE_ARCH_MMAP_RND_BITS + help + This value can be used to select the number of bits to use to + determine the random offset to the base address of vma regions + resulting from mmap allocations. This value will be bounded + by the architecture's minimum and maximum supported values. + + This value can be changed after boot using the + /proc/sys/vm/mmap_rnd_bits tunable + +config HAVE_ARCH_MMAP_RND_COMPAT_BITS + bool + help + An arch should select this symbol if it supports running applications + in compatibility mode, supports setting a variable number of bits for + use in establishing the base address for mmap allocations, has MMU + enabled and provides values for both: + - ARCH_MMAP_RND_COMPAT_BITS_MIN + - ARCH_MMAP_RND_COMPAT_BITS_MAX + +config ARCH_MMAP_RND_COMPAT_BITS_MIN + int + +config ARCH_MMAP_RND_COMPAT_BITS_MAX + int + +config ARCH_MMAP_RND_COMPAT_BITS_DEFAULT + int + +config ARCH_MMAP_RND_COMPAT_BITS + int "Number of bits to use for ASLR of mmap base address for compatible applications" if EXPERT + range ARCH_MMAP_RND_COMPAT_BITS_MIN ARCH_MMAP_RND_COMPAT_BITS_MAX + default ARCH_MMAP_RND_COMPAT_BITS_DEFAULT if ARCH_MMAP_RND_COMPAT_BITS_DEFAULT + default ARCH_MMAP_RND_COMPAT_BITS_MIN + depends on HAVE_ARCH_MMAP_RND_COMPAT_BITS + help + This value can be used to select the number of bits to use to + determine the random offset to the base address of vma regions + resulting from mmap allocations for compatible applications This + value will be bounded by the architecture's minimum and maximum + supported values. + + This value can be changed after boot using the + /proc/sys/vm/mmap_rnd_compat_bits tunable + source "kernel/gcov/Kconfig" diff --git a/include/linux/mm.h b/include/linux/mm.h index 328d55687eb0..138b14fc5cfe 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -43,6 +43,17 @@ extern int sysctl_legacy_va_layout; #define sysctl_legacy_va_layout 0 #endif +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS +extern const int mmap_rnd_bits_min; +extern const int mmap_rnd_bits_max; +extern int mmap_rnd_bits __read_mostly; +#endif +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS +extern const int mmap_rnd_compat_bits_min; +extern const int mmap_rnd_compat_bits_max; +extern int mmap_rnd_compat_bits __read_mostly; +#endif + #include #include #include diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 5b5777a20628..1ab135b96fef 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1382,6 +1382,28 @@ static struct ctl_table vm_table[] = { .extra1 = &zero, .extra2 = &one, }, +#endif +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS + { + .procname = "mmap_rnd_bits", + .data = &mmap_rnd_bits, + .maxlen = sizeof(mmap_rnd_bits), + .mode = 0600, + .proc_handler = proc_dointvec_minmax, + .extra1 = (void *)&mmap_rnd_bits_min, + .extra2 = (void *)&mmap_rnd_bits_max, + }, +#endif +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS + { + .procname = "mmap_rnd_compat_bits", + .data = &mmap_rnd_compat_bits, + .maxlen = sizeof(mmap_rnd_compat_bits), + .mode = 0600, + .proc_handler = proc_dointvec_minmax, + .extra1 = (void *)&mmap_rnd_compat_bits_min, + .extra2 = (void *)&mmap_rnd_compat_bits_max, + }, #endif { } }; diff --git a/mm/mmap.c b/mm/mmap.c index ded6fe9f144d..e495a844156e 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -46,6 +46,18 @@ #define arch_rebalance_pgtables(addr, len) (addr) #endif +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS +const int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN; +const int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX; +int mmap_rnd_bits __read_mostly = CONFIG_ARCH_MMAP_RND_BITS; +#endif +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS +const int mmap_rnd_compat_bits_min = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MIN; +const int mmap_rnd_compat_bits_max = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MAX; +int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS; +#endif + + static void unmap_region(struct mm_struct *mm, struct vm_area_struct *vma, struct vm_area_struct *prev, unsigned long start, unsigned long end);