From: Daniel Cashman <dcashman@android.com>
To: linux-kernel@vger.kernel.org
Cc: linux@arm.linux.org.uk, akpm@linux-foundation.org,
keescook@chromium.org, mingo@kernel.org,
linux-arm-kernel@lists.infradead.org, corbet@lwn.net,
dzickus@redhat.com, ebiederm@xmission.com, xypron.glpk@gmx.de,
jpoimboe@redhat.com, kirill.shutemov@linux.intel.com,
n-horiguchi@ah.jp.nec.com, aarcange@redhat.com, mgorman@suse.de,
tglx@linutronix.de, rientjes@google.com, linux-mm@kvack.org,
linux-doc@vger.kernel.org, salyzyn@android.com, jeffv@google.com,
nnk@google.com, dcashman <dcashman@google.com>
Subject: [PATCH v2 2/2] arm: mm: support ARCH_MMAP_RND_BITS.
Date: Tue, 3 Nov 2015 10:10:04 -0800 [thread overview]
Message-ID: <1446574204-15567-2-git-send-email-dcashman@android.com> (raw)
In-Reply-To: <1446574204-15567-1-git-send-email-dcashman@android.com>
From: dcashman <dcashman@google.com>
arm: arch_mmap_rnd() uses a hard-code value of 8 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 8 as the minimum acceptable value.
Signed-off-by: Daniel Cashman <dcashman@google.com>
---
Changes in v2:
- Changed arch/arm/Kconfig and arch/arm/mm/mmap.c to reflect changes
in [PATCH v2 1/2], specifically the movement of variables to global
rather than arch-specific files.
arch/arm/Kconfig | 10 ++++++++++
arch/arm/mm/mmap.c | 3 +--
2 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 639411f..47d7561 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -35,6 +35,7 @@ config ARM
select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32
select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32
+ select HAVE_ARCH_MMAP_RND_BITS
select HAVE_ARCH_SECCOMP_FILTER if (AEABI && !OABI_COMPAT)
select HAVE_ARCH_TRACEHOOK
select HAVE_BPF_JIT
@@ -306,6 +307,15 @@ config MMU
Select if you want MMU-based virtualised addressing space
support by paged memory management. If unsure, say 'Y'.
+config ARCH_MMAP_RND_BITS_MIN
+ default 8
+
+config ARCH_MMAP_RND_BITS_MAX
+ default 14 if MMU && PAGE_OFFSET=0x40000000
+ default 15 if MMU && PAGE_OFFSET=0x80000000
+ default 16 if MMU
+ default 8
+
#
# The "ARM system type" choice list is ordered alphabetically by option
# text. Please add new entries in the option alphabetic order.
diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
index 407dc78..c938693 100644
--- a/arch/arm/mm/mmap.c
+++ b/arch/arm/mm/mmap.c
@@ -173,8 +173,7 @@ unsigned long arch_mmap_rnd(void)
{
unsigned long rnd;
- /* 8 bits of randomness in 20 address space bits */
- rnd = (unsigned long)get_random_int() % (1 << 8);
+ rnd = (unsigned long)get_random_int() % (1 << mmap_rnd_bits);
return rnd << PAGE_SHIFT;
}
--
2.6.0.rc2.230.g3dd15c0
next prev parent reply other threads:[~2015-11-03 18:10 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-03 18:10 [PATCH v2 1/2] mm: mmap: Add new /proc tunable for mmap_base ASLR Daniel Cashman
2015-11-03 18:10 ` Daniel Cashman [this message]
2015-11-03 19:19 ` [PATCH v2 2/2] arm: mm: support ARCH_MMAP_RND_BITS Kees Cook
2015-11-03 22:39 ` Russell King - ARM Linux
2015-11-03 23:18 ` Kees Cook
2015-11-04 18:22 ` Daniel Cashman
2015-11-03 23:14 ` Daniel Cashman
2015-11-03 23:21 ` Kees Cook
2015-11-04 18:30 ` Daniel Cashman
2015-11-05 18:44 ` Daniel Cashman
2015-11-06 20:52 ` Kees Cook
2015-11-09 3:47 ` Michael Ellerman
2015-11-09 18:56 ` Daniel Cashman
2015-11-09 21:27 ` Kees Cook
2015-11-03 19:16 ` [PATCH v2 1/2] mm: mmap: Add new /proc tunable for mmap_base ASLR Kees Cook
2015-11-04 0:04 ` Andrew Morton
2015-11-04 0:40 ` Eric W. Biederman
2015-11-04 1:31 ` Andrew Morton
2015-11-04 19:31 ` Daniel Cashman
2015-11-04 22:00 ` Andrew Morton
2015-11-04 22:10 ` Eric W. Biederman
2015-11-04 22:37 ` Kees Cook
2015-11-04 9:39 ` Michal Hocko
2015-11-04 19:21 ` Eric W. Biederman
2015-11-04 19:36 ` Daniel Cashman
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