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Message-ID: <Pine.LNX.4.64.0802061442300.30955@jikos.suse.cz>
Date: Wed, 6 Feb 2008 14:45:26 +0100 (CET)
From: Jiri Kosina <jkosina@...e.cz>
To: Andrew Morton <akpm@...ux-foundation.org>
cc: Ingo Molnar <mingo@...e.hu>,
Arjan van de Ven <arjan@...radead.org>,
Randy Dunlap <randy.dunlap@...cle.com>,
Hugh Dickins <hugh@...itas.com>, Pavel Machek <pavel@....cz>,
linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] ASLR: add possibility for more fine-grained tweaking
From: Jiri Kosina <jkosina@...e.cz>
ASLR: add possibility for more fine-grained tweaking
Some prehistoric binaries don't like when start of brk area is located
anywhere else than just after code+bss.
This patch adds possibility to configure the default behavior of address
space randomization. In addition to that, randomize_va_space now can have
value of '2', which means full randomization including brk space.
Also, documentation of randomize_va_space is added.
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Arjan van de Ven <arjan@...radead.org>
Cc: Randy Dunlap <randy.dunlap@...cle.com>
Cc: Hugh Dickins <hugh@...itas.com>
Cc: Pavel Machek <pavel@....cz>
Signed-off-by: Jiri Kosina <jkosina@...e.cz>
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 8984a53..91ab40d 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -41,6 +41,7 @@ show up in /proc/sys/kernel:
- pid_max
- powersave-nap [ PPC only ]
- printk
+- randomize_va_space
- real-root-dev ==> Documentation/initrd.txt
- reboot-cmd [ SPARC only ]
- rtsig-max
@@ -280,6 +281,37 @@ send before ratelimiting kicks in.
==============================================================
+randomize-va-space:
+
+This option can be used to select the type of process address
+space randomization that is used in the system, for architectures
+that support this feature.
+
+One of the following numeric values is possible:
+
+0 - [none]
+ Turn the process address space randomization off by default.
+
+1 - [conservative]
+ Conservative address space randomization makes the addresses of
+ mmap base and VDSO page randomized. This, among other things,
+ implies that shared libraries will be loaded to random addresses.
+ Also for PIE binaries, the location of code start is randomized.
+
+2 - [full]
+
+ This includes all the features that Conservative randomization
+ provides. In addition to that, also start of the brk area is
+ randomized.
+ There a few legacy applications out there (such as some ancient
+ versions of libc.so.5 from 1996) that assume that brk area starts
+ just after the end of the code+bss. These applications break when
+ start of the brk area is randomized. There are however no known
+ non-legacy applications that would be broken this way, so for most
+ systems it is safe to choose Full randomization.
+
+==============================================================
+
reboot-cmd: (Sparc only)
??? This seems to be a way to give an argument to the Sparc
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 4628c42..d9f23d5 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1077,7 +1077,7 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
current->mm->start_stack = bprm->p;
#ifdef arch_randomize_brk
- if (current->flags & PF_RANDOMIZE)
+ if (current->flags & PF_RANDOMIZE && randomize_va_space == 2)
current->mm->brk = current->mm->start_brk =
arch_randomize_brk(current->mm);
#endif
diff --git a/init/Kconfig b/init/Kconfig
index 87f50df..aeb38b2 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -662,6 +662,46 @@ config SLOB
endchoice
+choice
+ prompt "Address space randomization type"
+ default RANDOMIZATION_CONSERVATIVE
+ help
+ This option allows to select the type of process address space
+ randomization that will be used by default (for those architectures
+ that support address space randomization). This option can be
+ overriden in runtime through kernel.randomize_va_space sysctl.
+
+config RANDOMIZATION_NONE
+ bool "NONE"
+ help
+ Turn the process address space randomization off by default.
+ Equivalent to sysctl kernel.randomize_va_space = 0.
+
+config RANDOMIZATION_CONSERVATIVE
+ bool "CONSERVATIVE"
+ help
+ Conservative address space randomization makes the addresses of
+ mmap base and VDSO page randomized. This, among other things,
+ implies that shared libraries will be loaded to random addresses.
+ Also for PIE binaries, the location of code start is randomized.
+ Equivalent to sysctl kernel.randomize_va_space = 1.
+
+config RANDOMIZATION_FULL
+ bool "FULL"
+ help
+ This includes all the features that Conservative randomization
+ provides. In addition to that, also start of the brk area is
+ randomized.
+ There a few legacy applications out there (such as some ancient
+ versions of libc.so.5 from 1996) that assume that the brk area
+ starts just after the end of the code+bss. These applications
+ break when start of the brk area is randomized. There are however
+ no known non-legacy applications that would be broken this way,
+ so for most systems it is safe to choose Full randomization.
+ Equivalent to sysctl kernel.randomize_va_space = 2.
+
+endchoice
+
config PROFILING
bool "Profiling support (EXPERIMENTAL)"
help
diff --git a/mm/memory.c b/mm/memory.c
index 7bb7072..e84f69a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -82,7 +82,15 @@ void * high_memory;
EXPORT_SYMBOL(num_physpages);
EXPORT_SYMBOL(high_memory);
+#ifdef CONFIG_RANDOMIZATION_CONSERVATIVE
int randomize_va_space __read_mostly = 1;
+#else
+#ifdef CONFIG_RANDOMIZATION_FULL
+int randomize_va_space __read_mostly = 2;
+#else
+int randomize_va_space __read_mostly = 0;
+#endif
+#endif
static int __init disable_randmaps(char *s)
{
--
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