From mboxrd@z Thu Jan 1 00:00:00 1970 From: dcashman@android.com (Daniel Cashman) Date: Wed, 18 Nov 2015 15:20:07 -0800 Subject: [PATCH v3 3/4] arm64: mm: support ARCH_MMAP_RND_BITS. In-Reply-To: <1447888808-31571-3-git-send-email-dcashman@android.com> References: <1447888808-31571-1-git-send-email-dcashman@android.com> <1447888808-31571-2-git-send-email-dcashman@android.com> <1447888808-31571-3-git-send-email-dcashman@android.com> Message-ID: <1447888808-31571-4-git-send-email-dcashman@android.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org From: dcashman 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 --- arch/arm64/Kconfig | 23 +++++++++++++++++++++++ arch/arm64/mm/mmap.c | 6 ++++-- 2 files changed, 27 insertions(+), 2 deletions(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 9ac16a4..be38e4c 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -51,6 +51,8 @@ config ARM64 select HAVE_ARCH_JUMP_LABEL select HAVE_ARCH_KASAN if SPARSEMEM_VMEMMAP select HAVE_ARCH_KGDB + select HAVE_ARCH_MMAP_RND_BITS + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT select HAVE_ARCH_SECCOMP_FILTER select HAVE_ARCH_TRACEHOOK select HAVE_BPF_JIT @@ -104,6 +106,27 @@ config ARCH_PHYS_ADDR_T_64BIT config MMU def_bool y +config ARCH_MMAP_RND_BITS_MIN + default 15 if ARM64_64K_PAGES + default 19 + +config ARCH_MMAP_RND_BITS_MAX + default 20 if ARM64_64K_PAGES && ARCH_VA_BITS=39 + default 24 if ARCH_VA_BITS=39 + default 23 if ARM64_64K_PAGES && ARCH_VA_BITS=42 + default 27 if ARCH_VA_BITS=42 + default 29 if ARM64_64K_PAGES && ARCH_VA_BITS=48 + default 33 if ARCH_VA_BITS=48 + default 15 if ARM64_64K_PAGES + default 19 + +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 NO_IOPORT_MAP def_bool y if !PCI diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c index ed17747..b84d5b1 100644 --- a/arch/arm64/mm/mmap.c +++ b/arch/arm64/mm/mmap.c @@ -51,8 +51,10 @@ unsigned long arch_mmap_rnd(void) { unsigned long rnd; - rnd = (unsigned long)get_random_int() & STACK_RND_MASK; - + if (test_thread_flag(TIF_32BIT)) + rnd = (unsigned long)get_random_int() % (1 << mmap_rnd_compat_bits); + else + rnd = (unsigned long)get_random_int() % (1 << mmap_rnd_bits); return rnd << PAGE_SHIFT; } -- 2.6.0.rc2.230.g3dd15c0