LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Jiri Kosina <jkosina@suse.cz>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>,
	Arjan van de Ven <arjan@infradead.org>,
	Randy Dunlap <randy.dunlap@oracle.com>,
	Hugh Dickins <hugh@veritas.com>, Pavel Machek <pavel@ucw.cz>,
	linux-kernel@vger.kernel.org
Subject: [PATCH 2/2] ASLR: add possibility for more fine-grained tweaking
Date: Wed, 6 Feb 2008 14:45:26 +0100 (CET)	[thread overview]
Message-ID: <Pine.LNX.4.64.0802061442300.30955@jikos.suse.cz> (raw)
In-Reply-To: <Pine.LNX.4.64.0802061438150.30955@jikos.suse.cz>

From: Jiri Kosina <jkosina@suse.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@elte.hu>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.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)
 {

  parent reply	other threads:[~2008-02-06 13:46 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-06 13:45 [PATCH 0/2] brk and randomization fixes Jiri Kosina
2008-02-06 13:45 ` [PATCH 1/2] brk: check the lower bound properly Jiri Kosina
2008-02-06 13:45 ` Jiri Kosina [this message]
2008-02-06 13:49   ` [PATCH 2/2] ASLR: add possibility for more fine-grained tweaking Ingo Molnar
2008-02-06 16:26     ` [PATCH] Document randomize_va_space and CONFIG_COMPAT_BRK (was Re: [PATCH 2/2] ASLR: add possibility for more fine-grained tweaking) Jiri Kosina
2008-02-06 23:10       ` Ingo Molnar
2008-02-07  9:49         ` Jiri Kosina
2008-02-07 14:30         ` Jiri Kosina
2008-02-07 15:01           ` Ingo Molnar
2008-02-07 10:23     ` [PATCH 2/2] ASLR: add possibility for more fine-grained tweaking Geert Uytterhoeven
2008-02-07 10:31       ` Ismail Dönmez
2008-02-07 10:32       ` Ingo Molnar
2008-02-07 10:43         ` Geert Uytterhoeven

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=Pine.LNX.4.64.0802061442300.30955@jikos.suse.cz \
    --to=jkosina@suse.cz \
    --cc=akpm@linux-foundation.org \
    --cc=arjan@infradead.org \
    --cc=hugh@veritas.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@elte.hu \
    --cc=pavel@ucw.cz \
    --cc=randy.dunlap@oracle.com \
    --subject='Re: [PATCH 2/2] ASLR: add possibility for more fine-grained tweaking' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).