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| author | dcashman <dcashman@google.com> | 2015-12-29 15:44:12 -0800 |
|---|---|---|
| committer | Kees Cook <keescook@google.com> | 2016-03-24 15:25:46 -0700 |
| commit | 4cc67625ef415ad32020e75fa5f612dcd51ee74c (patch) | |
| tree | dc918544f468576f10aa557cab1037770213facd | |
| parent | bbdd420328a3b94c64397954943d62ef63a4ad3c (diff) | |
| download | pxa-v3.14-4cc67625ef415ad32020e75fa5f612dcd51ee74c.tar.gz | |
FROMLIST: x86: mm: support ARCH_MMAP_RND_BITS.
(cherry picked from commit https://lkml.org/lkml/2015/12/21/339)
x86: arch_mmap_rnd() uses hard-coded values, 8 for 32-bit and 28 for
64-bit, to generate the random offset for the mmap base address.
This value represents a compromise between increased ASLR
effectiveness and avoiding address-space fragmentation. Replace it
with a Kconfig option, which is sensibly bounded, so that platform
developers may choose where to place this compromise. Keep default
values as new minimums.
Signed-off-by: Daniel Cashman <dcashman@android.com>
Signed-off-by: Daniel Cashman <dcashman@google.com>
Bug: 27796957
Patchset: ASLR sysctl
Change-Id: I65e14a627f2b370566652f569b07e4327d9e42df
Signed-off-by: Kees Cook <keescook@google.com>
| -rw-r--r-- | arch/x86/Kconfig | 16 | ||||
| -rw-r--r-- | arch/x86/mm/mmap.c | 12 |
2 files changed, 22 insertions, 6 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 2f645c90e4d..f92353ae83c 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -101,6 +101,8 @@ config X86 select DCACHE_WORD_ACCESS select GENERIC_SMP_IDLE_THREAD select ARCH_WANT_IPC_PARSE_VERSION if X86_32 + select HAVE_ARCH_MMAP_RND_BITS if MMU + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT select HAVE_ARCH_SECCOMP_FILTER select BUILDTIME_EXTABLE_SORT select GENERIC_CMOS_UPDATE @@ -155,6 +157,20 @@ config HAVE_LATENCYTOP_SUPPORT config MMU def_bool y +config ARCH_MMAP_RND_BITS_MIN + default 28 if 64BIT + default 8 + +config ARCH_MMAP_RND_BITS_MAX + default 32 if 64BIT + default 16 + +config ARCH_MMAP_RND_COMPAT_BITS_MIN + default 8 + +config ARCH_MMAP_RND_COMPAT_BITS_MAX + default 16 + config SBUS bool diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index 3601ff284b9..7c8a3f74957 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -69,15 +69,15 @@ static unsigned long mmap_rnd(void) { unsigned long rnd = 0; - /* - * 8 bits of randomness in 32bit mmaps, 20 address space bits - * 28 bits of randomness in 64bit mmaps, 40 address space bits - */ if (current->flags & PF_RANDOMIZE) { if (mmap_is_ia32()) - rnd = get_random_int() % (1<<8); +#ifdef CONFIG_COMPAT + rnd = (unsigned long)get_random_int() & ((1 << mmap_rnd_compat_bits) - 1); +#else + rnd = (unsigned long)get_random_int() & ((1 << mmap_rnd_bits) - 1); +#endif else - rnd = get_random_int() % (1<<28); + rnd = (unsigned long)get_random_int() & ((1 << mmap_rnd_bits) - 1); } return rnd << PAGE_SHIFT; } |