[PATCH v3 3/4] arm64: mm: support ARCH_MMAP_RND_BITS.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



From: dcashman <dcashman@xxxxxxxxxx>

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@xxxxxxxxxx>
---
 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

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>



[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux]     [Linux OMAP]     [Linux MIPS]     [ECOS]     [Asterisk Internet PBX]     [Linux API]