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authorEric Paris <eparis@redhat.com>2009-07-31 12:54:11 -0400
committerJames Morris <jmorris@namei.org>2009-08-17 15:09:11 +1000
commit788084aba2ab7348257597496befcbccabdc98a3 (patch)
tree2da42d746d67b16ef705229a1b5a3528ec19c725
parent8cf948e744e0218af604c32edecde10006dc8e9e (diff)
downloadconfigs-788084aba2ab7348257597496befcbccabdc98a3.tar.gz
Security/SELinux: seperate lsm specific mmap_min_addr
Currently SELinux enforcement of controls on the ability to map low memory is determined by the mmap_min_addr tunable. This patch causes SELinux to ignore the tunable and instead use a seperate Kconfig option specific to how much space the LSM should protect. The tunable will now only control the need for CAP_SYS_RAWIO and SELinux permissions will always protect the amount of low memory designated by CONFIG_LSM_MMAP_MIN_ADDR. This allows users who need to disable the mmap_min_addr controls (usual reason being they run WINE as a non-root user) to do so and still have SELinux controls preventing confined domains (like a web server) from being able to map some area of low memory. Signed-off-by: Eric Paris <eparis@redhat.com> Signed-off-by: James Morris <jmorris@namei.org>
-rw-r--r--include/linux/mm.h15
-rw-r--r--include/linux/security.h17
-rw-r--r--kernel/sysctl.c7
-rw-r--r--mm/Kconfig6
-rw-r--r--mm/mmap.c3
-rw-r--r--mm/nommu.c3
-rw-r--r--security/Kconfig16
-rw-r--r--security/Makefile2
-rw-r--r--security/commoncap.c2
-rw-r--r--security/min_addr.c49
-rw-r--r--security/selinux/hooks.c2
11 files changed, 92 insertions, 30 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h
index ba3a7cb1eaa..9a72cc78e6b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -34,8 +34,6 @@ extern int sysctl_legacy_va_layout;
#define sysctl_legacy_va_layout 0
#endif
-extern unsigned long mmap_min_addr;
-
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/processor.h>
@@ -575,19 +573,6 @@ static inline void set_page_links(struct page *page, enum zone_type zone,
}
/*
- * If a hint addr is less than mmap_min_addr change hint to be as
- * low as possible but still greater than mmap_min_addr
- */
-static inline unsigned long round_hint_to_min(unsigned long hint)
-{
- hint &= PAGE_MASK;
- if (((void *)hint != NULL) &&
- (hint < mmap_min_addr))
- return PAGE_ALIGN(mmap_min_addr);
- return hint;
-}
-
-/*
* Some inline functions in vmstat.h depend on page_zone()
*/
#include <linux/vmstat.h>
diff --git a/include/linux/security.h b/include/linux/security.h
index ac4bc3760b4..dc3472c1f78 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -28,6 +28,7 @@
#include <linux/resource.h>
#include <linux/sem.h>
#include <linux/shm.h>
+#include <linux/mm.h> /* PAGE_ALIGN */
#include <linux/msg.h>
#include <linux/sched.h>
#include <linux/key.h>
@@ -95,6 +96,7 @@ extern int cap_netlink_send(struct sock *sk, struct sk_buff *skb);
extern int cap_netlink_recv(struct sk_buff *skb, int cap);
extern unsigned long mmap_min_addr;
+extern unsigned long dac_mmap_min_addr;
/*
* Values used in the task_security_ops calls
*/
@@ -147,6 +149,21 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
opts->num_mnt_opts = 0;
}
+/*
+ * If a hint addr is less than mmap_min_addr change hint to be as
+ * low as possible but still greater than mmap_min_addr
+ */
+static inline unsigned long round_hint_to_min(unsigned long hint)
+{
+ hint &= PAGE_MASK;
+ if (((void *)hint != NULL) &&
+ (hint < mmap_min_addr))
+ return PAGE_ALIGN(mmap_min_addr);
+ return hint;
+}
+
+extern int mmap_min_addr_handler(struct ctl_table *table, int write, struct file *filp,
+ void __user *buffer, size_t *lenp, loff_t *ppos);
/**
* struct security_operations - main security structure
*
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 98e02328c67..58be76017fd 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -49,6 +49,7 @@
#include <linux/acpi.h>
#include <linux/reboot.h>
#include <linux/ftrace.h>
+#include <linux/security.h>
#include <linux/slow-work.h>
#include <linux/perf_counter.h>
@@ -1306,10 +1307,10 @@ static struct ctl_table vm_table[] = {
{
.ctl_name = CTL_UNNUMBERED,
.procname = "mmap_min_addr",
- .data = &mmap_min_addr,
- .maxlen = sizeof(unsigned long),
+ .data = &dac_mmap_min_addr,
+ .maxlen = sizeof(unsigned long),
.mode = 0644,
- .proc_handler = &proc_doulongvec_minmax,
+ .proc_handler = &mmap_min_addr_handler,
},
#ifdef CONFIG_NUMA
{
diff --git a/mm/Kconfig b/mm/Kconfig
index c948d4ca8bd..fe5f674d7a7 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -225,9 +225,9 @@ config DEFAULT_MMAP_MIN_ADDR
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.
+ Programs which use vm86 functionality or have some need to map
+ this low address space will need CAP_SYS_RAWIO or disable this
+ protection by setting the value to 0.
This value can be changed after boot using the
/proc/sys/vm/mmap_min_addr tunable.
diff --git a/mm/mmap.c b/mm/mmap.c
index 34579b23ebd..8101de490c7 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -88,9 +88,6 @@ int sysctl_overcommit_ratio = 50; /* default is 50% */
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
diff --git a/mm/nommu.c b/mm/nommu.c
index 53cab10fece..28754c40be9 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -69,9 +69,6 @@ int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT;
int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
int heap_stack_gap = 0;
-/* amount of vm to protect from userspace access */
-unsigned long mmap_min_addr = CONFIG_DEFAULT_MMAP_MIN_ADDR;
-
atomic_long_t mmap_pages_allocated;
EXPORT_SYMBOL(mem_map);
diff --git a/security/Kconfig b/security/Kconfig
index d23c839038f..9c60c346a91 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -113,6 +113,22 @@ config SECURITY_ROOTPLUG
If you are unsure how to answer this question, answer N.
+config LSM_MMAP_MIN_ADDR
+ int "Low address space for LSM to from user allocation"
+ depends on SECURITY && SECURITY_SELINUX
+ default 65535
+ 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 or have some need to map
+ this low address space will need the permission specific to the
+ systems running LSM.
+
source security/selinux/Kconfig
source security/smack/Kconfig
source security/tomoyo/Kconfig
diff --git a/security/Makefile b/security/Makefile
index c67557cdaa8..b56e7f9ecbc 100644
--- a/security/Makefile
+++ b/security/Makefile
@@ -8,7 +8,7 @@ subdir-$(CONFIG_SECURITY_SMACK) += smack
subdir-$(CONFIG_SECURITY_TOMOYO) += tomoyo
# always enable default capabilities
-obj-y += commoncap.o
+obj-y += commoncap.o min_addr.o
# Object file lists
obj-$(CONFIG_SECURITY) += security.o capability.o
diff --git a/security/commoncap.c b/security/commoncap.c
index 6bcf6e81e54..e3097c0a131 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -1005,7 +1005,7 @@ int cap_file_mmap(struct file *file, unsigned long reqprot,
{
int ret = 0;
- if (addr < mmap_min_addr) {
+ if (addr < dac_mmap_min_addr) {
ret = cap_capable(current, current_cred(), CAP_SYS_RAWIO,
SECURITY_CAP_AUDIT);
/* set PF_SUPERPRIV if it turns out we allow the low mmap */
diff --git a/security/min_addr.c b/security/min_addr.c
new file mode 100644
index 00000000000..14cc7b3b8d0
--- /dev/null
+++ b/security/min_addr.c
@@ -0,0 +1,49 @@
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/security.h>
+#include <linux/sysctl.h>
+
+/* amount of vm to protect from userspace access by both DAC and the LSM*/
+unsigned long mmap_min_addr;
+/* amount of vm to protect from userspace using CAP_SYS_RAWIO (DAC) */
+unsigned long dac_mmap_min_addr = CONFIG_DEFAULT_MMAP_MIN_ADDR;
+/* amount of vm to protect from userspace using the LSM = CONFIG_LSM_MMAP_MIN_ADDR */
+
+/*
+ * Update mmap_min_addr = max(dac_mmap_min_addr, CONFIG_LSM_MMAP_MIN_ADDR)
+ */
+static void update_mmap_min_addr(void)
+{
+#ifdef CONFIG_LSM_MMAP_MIN_ADDR
+ if (dac_mmap_min_addr > CONFIG_LSM_MMAP_MIN_ADDR)
+ mmap_min_addr = dac_mmap_min_addr;
+ else
+ mmap_min_addr = CONFIG_LSM_MMAP_MIN_ADDR;
+#else
+ mmap_min_addr = dac_mmap_min_addr;
+#endif
+}
+
+/*
+ * sysctl handler which just sets dac_mmap_min_addr = the new value and then
+ * calls update_mmap_min_addr() so non MAP_FIXED hints get rounded properly
+ */
+int mmap_min_addr_handler(struct ctl_table *table, int write, struct file *filp,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ int ret;
+
+ ret = proc_doulongvec_minmax(table, write, filp, buffer, lenp, ppos);
+
+ update_mmap_min_addr();
+
+ return ret;
+}
+
+int __init init_mmap_min_addr(void)
+{
+ update_mmap_min_addr();
+
+ return 0;
+}
+pure_initcall(init_mmap_min_addr);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index e6d1432b080..8d8b69c5664 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3036,7 +3036,7 @@ static int selinux_file_mmap(struct file *file, unsigned long reqprot,
* at bad behaviour/exploit that we always want to get the AVC, even
* if DAC would have also denied the operation.
*/
- if (addr < mmap_min_addr) {
+ if (addr < CONFIG_LSM_MMAP_MIN_ADDR) {
rc = avc_has_perm(sid, sid, SECCLASS_MEMPROTECT,
MEMPROTECT__MMAP_ZERO, NULL);
if (rc)