[patch 02/24] security: use mmap_min_addr indepedently of security models

Greg KH
2009-07-17T20:23:49Z

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2.6.30-stable review patch. If anyone has any objections, please let us know.

------------------

From: Christoph Lameter <cl@linux-foundation.org>

commit e0a94c2a63f2644826069044649669b5e7ca75d3 upstream.

This patch removes the dependency of mmap_min_addr on CONFIG_SECURITY.
It also sets a default mmap_min_addr of 4096.

mmapping of addresses below 4096 will only be possible for processes
with CAP_SYS_RAWIO.

Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Acked-by: Eric Paris <eparis@redhat.com>
Looks-ok-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: James Morris <jmorris@namei.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
include/linux/mm.h | 2 --
include/linux/security.h | 2 ++
kernel/sysctl.c | 2 --
mm/Kconfig | 19 +++++++++++++++++++
mm/mmap.c | 3 +++
security/Kconfig | 22 +---------------------
security/security.c | 3 ---
7 files changed, 25 insertions(+), 28 deletions(-)

--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -580,12 +580,10 @@ static inline void set_page_links(struct
*/
static inline unsigned long round_hint_to_min(unsigned long hint)
{
-#ifdef CONFIG_SECURITY
hint &= PAGE_MASK;
if (((void *)hint != NULL) &&
(hint < mmap_min_addr))
return PAGE_ALIGN(mmap_min_addr);
-#endif
return hint;
}

--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -2197,6 +2197,8 @@ static inline int security_file_mmap(str
unsigned long addr,
unsigned long addr_only)
{
+ if ((addr < mmap_min_addr) && !capable(CAP_SYS_RAWIO))
+ return -EACCES;
return 0;
}

--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1225,7 +1225,6 @@ static struct ctl_table vm_table[] = {
.strategy = &sysctl_jiffies,
},
#endif
-#ifdef CONFIG_SECURITY
{
.ctl_name = CTL_UNNUMBERED,
.procname = "mmap_min_addr",
@@ -1234,7 +1233,6 @@ static struct ctl_table vm_table[] = {
.mode = 0644,
.proc_handler = &proc_doulongvec_minmax,
},
-#endif
#ifdef CONFIG_NUMA
{
.ctl_name = CTL_UNNUMBERED,
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -226,6 +226,25 @@ config HAVE_MLOCKED_PAGE_BIT
config MMU_NOTIFIER
bool

+config DEFAULT_MMAP_MIN_ADDR
+ int "Low address space to protect from user allocation"
+ default 4096
+ help
+ This is the portion of low virtual memory which should be protected
+ from userspace allocation. Keeping a user from writing to low pages
+ can help reduce the impact of kernel NULL pointer bugs.
+
+ For most ia64, ppc64 and x86 users with lots of address space
+ a value of 65536 is reasonable and should cause no problems.
+ On arm and other archs it should not be higher than 32768.
+ Programs which use vm86 functionality would either need additional
+ permissions from either the LSM or the capabilities module or have
+ this protection disabled.
+
+ This value can be changed after boot using the
+ /proc/sys/vm/mmap_min_addr tunable.
+
+
config NOMMU_INITIAL_TRIM_EXCESS
int "Turn on mmap() excess space trimming before booting"
depends on !MMU
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -87,6 +87,9 @@ int sysctl_overcommit_ratio = 50; /* def
int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
struct percpu_counter vm_committed_as;

+/* amount of vm to protect from userspace access */
+unsigned long mmap_min_addr = CONFIG_DEFAULT_MMAP_MIN_ADDR;
+
/*
* Check that a process has enough memory to allocate a new virtual
* mapping. 0 means there is enough memory for the allocation to
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -110,28 +110,8 @@ config SECURITY_ROOTPLUG

See <http://www.linuxjournal.com/article.php?sid=6279> for
more information about this module.
-
- If you are unsure how to answer this question, answer N.
-
-config SECURITY_DEFAULT_MMAP_MIN_ADDR
- int "Low address space to protect from user allocation"
- depends on SECURITY
- default 0
- help
- This is the portion of low virtual memory which should be protected
- from userspace allocation. Keeping a user from writing to low pages
- can help reduce the impact of kernel NULL pointer bugs.
-
- For most ia64, ppc64 and x86 users with lots of address space
- a value of 65536 is reasonable and should cause no problems.
- On arm and other archs it should not be higher than 32768.
- Programs which use vm86 functionality would either need additional
- permissions from either the LSM or the capabilities module or have
- this protection disabled.
-
- This value can be changed after boot using the
- /proc/sys/vm/mmap_min_addr tunable.

+ If you are unsure how to answer this question, answer N.

source security/selinux/Kconfig
source security/smack/Kconfig
--- a/security/security.c
+++ b/security/security.c
@@ -26,9 +26,6 @@ extern void security_fixup_ops(struct se

struct security_operations *security_ops; /* Initialized to NULL */

-/* amount of vm to protect from userspace access */
-unsigned long mmap_min_addr = CONFIG_SECURITY_DEFAULT_MMAP_MIN_ADDR;
-
static inline int verify(struct security_operations *ops)
{
/* verify the security_operations structure exists */