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| author | dcashman <dcashman@google.com> | 2015-12-29 15:28:13 -0800 |
|---|---|---|
| committer | Kees Cook <keescook@google.com> | 2016-03-24 15:02:01 -0700 |
| commit | b5b808da5e294a9ff28d607249b65da8a26b3c01 (patch) | |
| tree | a0bfda07e793e34538a7a0680bfaed1ae62814cb | |
| parent | 342c95721fa3e17c205e1735693046e4cd05674b (diff) | |
| download | picoimx-3.14-b5b808da5e294a9ff28d607249b65da8a26b3c01.tar.gz | |
BACKPORT: FROMLIST: arm64: mm: support ARCH_MMAP_RND_BITS.
(cherry picked from commit https://lkml.org/lkml/2015/12/21/340)
arm64: arch_mmap_rnd() uses STACK_RND_MASK 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: Ic81409f45c8025c63419558df8b43ec9ec478082
Signed-off-by: Kees Cook <keescook@google.com>
| -rw-r--r-- | arch/arm64/Kconfig | 21 | ||||
| -rw-r--r-- | arch/arm64/mm/mmap.c | 11 |
2 files changed, 29 insertions, 3 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 372eb823e92..4e42f602eca 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -32,6 +32,8 @@ config ARM64 select HARDIRQS_SW_RESEND select HAVE_ARCH_JUMP_LABEL select HAVE_ARCH_KGDB + select HAVE_ARCH_MMAP_RND_BITS + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT select HAVE_ARCH_TRACEHOOK select HAVE_C_RECORDMCOUNT select HAVE_DEBUG_BUGVERBOSE @@ -358,6 +360,25 @@ config HW_PERF_EVENTS config SYS_SUPPORTS_HUGETLBFS def_bool y +config ARCH_MMAP_RND_BITS_MIN + default 14 if ARM64_64K_PAGES + default 18 + +# max bits determined by the following formula: +# VA_BITS - PAGE_SHIFT - 3 +# VA_BITS depends on 64K_PAGES, either +# 42 if 64K_PAGES or 39 otherwise +config ARCH_MMAP_RND_BITS_MAX + default 23 if ARM64_64K_PAGES + default 24 + +config ARCH_MMAP_RND_COMPAT_BITS_MIN + default 7 if ARM64_64K_PAGES + default 11 + +config ARCH_MMAP_RND_COMPAT_BITS_MAX + default 16 + config ARCH_WANT_GENERAL_HUGETLB def_bool y diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c index 8f7ffffc63e..ab79843410a 100644 --- a/arch/arm64/mm/mmap.c +++ b/arch/arm64/mm/mmap.c @@ -51,9 +51,14 @@ static unsigned long mmap_rnd(void) { unsigned long rnd = 0; - if (current->flags & PF_RANDOMIZE) - rnd = (long)get_random_int() & STACK_RND_MASK; - + if (current->flags & PF_RANDOMIZE) { +#ifdef CONFIG_COMPAT + if (test_thread_flag(TIF_32BIT)) + rnd = (unsigned long)get_random_int() & ((1 << mmap_rnd_compat_bits) - 1); + else +#endif + rnd = (unsigned long)get_random_int() & ((1 << mmap_rnd_bits) - 1); + } return rnd << PAGE_SHIFT; } |