diff options
| author | dcashman <dcashman@google.com> | 2015-12-29 15:44:12 -0800 |
|---|---|---|
| committer | Kees Cook <keescook@google.com> | 2016-03-24 15:32:06 -0700 |
| commit | 113b124387d69a2771fbd80cb8155d556ba0f60b (patch) | |
| tree | f3b2902cc34603856ad5dbfcf2fc16ba7c7c77f1 | |
| parent | 08456f54219660d0e84039e07af22a72304f19fe (diff) | |
| download | edison-v3.10-113b124387d69a2771fbd80cb8155d556ba0f60b.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: I0270b0e837c0fe7284d79c5dafe91e998c15a715
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 aee32eedc1a..f0f33ae4504 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -99,6 +99,8 @@ 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 @@ -149,6 +151,20 @@ 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 75f9e5d80d0..8ba10d84ed4 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; } |