diff options
| author | dcashman <dcashman@google.com> | 2015-12-29 15:28:13 -0800 |
|---|---|---|
| committer | Moyster <oysterized@gmail.com> | 2016-09-10 16:51:13 +0200 |
| commit | ec3bb9c30fda6f9313e119d5c9fcb8a7097c677b (patch) | |
| tree | f9493d86d0d36146aeed0afcdd5e677249ebe783 | |
| parent | 53d1ed7798ca6200040c0052121efbafe1874594 (diff) | |
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.
Bug: 24047224
Signed-off-by: Daniel Cashman <dcashman@android.com>
Signed-off-by: Daniel Cashman <dcashman@google.com>
Change-Id: I7caf105b838cfc3ab55f275e1a061eb2b77c9a2a
| -rw-r--r-- | arch/arm64/Kconfig | 19 | ||||
| -rw-r--r-- | arch/arm64/mm/mmap.c | 11 |
2 files changed, 27 insertions, 3 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 1d4b6e08e..ff50d39c3 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -23,6 +23,8 @@ config ARM64 select HARDIRQS_SW_RESEND select HAVE_ARCH_JUMP_LABEL select HAVE_ARCH_AUDITSYSCALL + select HAVE_ARCH_MMAP_RND_BITS + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT select HAVE_ARCH_SECCOMP_FILTER select HAVE_ARCH_KGDB select HAVE_ARCH_TRACEHOOK @@ -75,6 +77,23 @@ config NO_IOPORT config STACKTRACE_SUPPORT 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 is always 39 +config ARCH_MMAP_RND_BITS_MAX + default 20 if ARM64_64K_PAGES + default 24 + +config ARCH_MMAP_RND_COMPAT_BITS_MIN + default 11 + +config ARCH_MMAP_RND_COMPAT_BITS_MAX + default 16 + config ILLEGAL_POINTER_VALUE hex default 0xdead000000000000 diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c index 8aaf073ee..8af07b65e 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; } |