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.

Eric Paris committed 17 years ago

Commit 788084a1 parent 8cf948e11 files · +92 −30Browse files

Unified · Split

11 files

include/linux/mm.h +0 −15
include/linux/security.h +17 −0
kernel/sysctl.c +4 −3
mm/Kconfig +3 −3
mm/mmap.c +0 −3
mm/nommu.c +0 −3
security/Kconfig +16 −0
security/Makefile +1 −1
security/commoncap.c +1 −1
security/min_addr.c +49 −0
security/selinux/hooks.c +1 −1

include/linux/mm.h+0−15

@@ -34,8 +34,6 @@ extern int sysctl_legacy_va_layout; · 33 unmodified lines
34	34	#define sysctl_legacy_va_layout 0
35	35	#endif
36	36
37		−extern unsigned long mmap_min_addr;
38		−
39	37	#include <asm/page.h>
40	38	#include <asm/pgtable.h>
41	39	#include <asm/processor.h>
@@ -574,19 +572,6 @@ static inline void set_page_links(struct page *page, enum zone_type zone, · 532 unmodified lines
574	572	set_page_section(page, pfn_to_section_nr(pfn));
575	573	}
576	574
577		−/*
578		− * If a hint addr is less than mmap_min_addr change hint to be as
579		− * low as possible but still greater than mmap_min_addr
580		− */
581		−static inline unsigned long round_hint_to_min(unsigned long hint)
582		−{
583		− hint &= PAGE_MASK;
584		− if (((void *)hint != NULL) &&
585		− (hint < mmap_min_addr))
586		− return PAGE_ALIGN(mmap_min_addr);
587		− return hint;
588		−}
589		−
590	575	/*
591	576	* Some inline functions in vmstat.h depend on page_zone()
592	577	*/

include/linux/security.h+17−0

@@ -28,6 +28,7 @@ · 27 unmodified lines
28	28	#include <linux/resource.h>
29	29	#include <linux/sem.h>
30	30	#include <linux/shm.h>
	31	+#include <linux/mm.h> /* PAGE_ALIGN */
31	32	#include <linux/msg.h>
32	33	#include <linux/sched.h>
33	34	#include <linux/key.h>
@@ -95,6 +96,7 @@ extern int cap_netlink_send(struct sock sk, struct sk_buff skb); · 61 unmodified lines
95	96	extern int cap_netlink_recv(struct sk_buff *skb, int cap);
96	97
97	98	extern unsigned long mmap_min_addr;
	99	+extern unsigned long dac_mmap_min_addr;
98	100	/*
99	101	* Values used in the task_security_ops calls
100	102	*/
@@ -147,6 +149,21 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts) · 46 unmodified lines
147	149	opts->num_mnt_opts = 0;
148	150	}
149	151
	152	+/*
	153	+ * If a hint addr is less than mmap_min_addr change hint to be as
	154	+ * low as possible but still greater than mmap_min_addr
	155	+ */
	156	+static inline unsigned long round_hint_to_min(unsigned long hint)
	157	+{
	158	+ hint &= PAGE_MASK;
	159	+ if (((void *)hint != NULL) &&
	160	+ (hint < mmap_min_addr))
	161	+ return PAGE_ALIGN(mmap_min_addr);
	162	+ return hint;
	163	+}
	164	+
	165	+extern int mmap_min_addr_handler(struct ctl_table table, int write, struct file filp,
	166	+ void __user buffer, size_t lenp, loff_t *ppos);
150	167	/**
151	168	* struct security_operations - main security structure
152	169	*

kernel/sysctl.c+4−3

@@ -49,6 +49,7 @@ · 48 unmodified lines
49	49	#include <linux/acpi.h>
50	50	#include <linux/reboot.h>
51	51	#include <linux/ftrace.h>
	52	+#include <linux/security.h>
52	53	#include <linux/slow-work.h>
53	54	#include <linux/perf_counter.h>
54	55
@@ -1306,10 +1307,10 @@ static struct ctl_table vm_table[] = { · 1251 unmodified lines
1306	1307	{
1307	1308	.ctl_name = CTL_UNNUMBERED,
1308	1309	.procname = "mmap_min_addr",
1309		− .data = &mmap_min_addr,
1310		− .maxlen = sizeof(unsigned long),
	1310	+ .data = &dac_mmap_min_addr,
	1311	+ .maxlen = sizeof(unsigned long),
1311	1312	.mode = 0644,
1312		− .proc_handler = &proc_doulongvec_minmax,
	1313	+ .proc_handler = &mmap_min_addr_handler,
1313	1314	},
1314	1315	#ifdef CONFIG_NUMA
1315	1316	{

mm/Kconfig+3−3

@@ -225,9 +225,9 @@ config DEFAULT_MMAP_MIN_ADDR · 224 unmodified lines
225	225	For most ia64, ppc64 and x86 users with lots of address space
226	226	a value of 65536 is reasonable and should cause no problems.
227	227	On arm and other archs it should not be higher than 32768.
228		− Programs which use vm86 functionality would either need additional
229		− permissions from either the LSM or the capabilities module or have
230		− this protection disabled.
	228	+ Programs which use vm86 functionality or have some need to map
	229	+ this low address space will need CAP_SYS_RAWIO or disable this
	230	+ protection by setting the value to 0.
231	231
232	232	This value can be changed after boot using the
233	233	/proc/sys/vm/mmap_min_addr tunable.

mm/mmap.c+0−3

@@ -88,9 +88,6 @@ int sysctl_overcommit_ratio = 50; /* default is 50% */ · 87 unmodified lines
88	88	int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
89	89	struct percpu_counter vm_committed_as;
90	90
91		−/* amount of vm to protect from userspace access */
92		−unsigned long mmap_min_addr = CONFIG_DEFAULT_MMAP_MIN_ADDR;
93		−
94	91	/*
95	92	* Check that a process has enough memory to allocate a new virtual
96	93	* mapping. 0 means there is enough memory for the allocation to

mm/nommu.c+0−3

@@ -69,9 +69,6 @@ int sysctl_max_map_count = DEFAULT_MAX_MAP_COUNT; · 68 unmodified lines
69	69	int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
70	70	int heap_stack_gap = 0;
71	71
72		−/* amount of vm to protect from userspace access */
73		−unsigned long mmap_min_addr = CONFIG_DEFAULT_MMAP_MIN_ADDR;
74		−
75	72	atomic_long_t mmap_pages_allocated;
76	73
77	74	EXPORT_SYMBOL(mem_map);

security/Kconfig+16−0

@@ -113,6 +113,22 @@ config SECURITY_ROOTPLUG · 112 unmodified lines
113	113
114	114	If you are unsure how to answer this question, answer N.
115	115
	116	+config LSM_MMAP_MIN_ADDR
	117	+ int "Low address space for LSM to from user allocation"
	118	+ depends on SECURITY && SECURITY_SELINUX
	119	+ default 65535
	120	+ help
	121	+ This is the portion of low virtual memory which should be protected
	122	+ from userspace allocation. Keeping a user from writing to low pages
	123	+ can help reduce the impact of kernel NULL pointer bugs.
	124	+
	125	+ For most ia64, ppc64 and x86 users with lots of address space
	126	+ a value of 65536 is reasonable and should cause no problems.
	127	+ On arm and other archs it should not be higher than 32768.
	128	+ Programs which use vm86 functionality or have some need to map
	129	+ this low address space will need the permission specific to the
	130	+ systems running LSM.
	131	+
116	132	source security/selinux/Kconfig
117	133	source security/smack/Kconfig
118	134	source security/tomoyo/Kconfig

security/Makefile+1−1

@@ -8,7 +8,7 @@ subdir-$(CONFIG_SECURITY_SMACK) += smack · 7 unmodified lines
8	8	subdir-$(CONFIG_SECURITY_TOMOYO) += tomoyo
9	9
10	10	# always enable default capabilities
11		−obj-y += commoncap.o
	11	+obj-y += commoncap.o min_addr.o
12	12
13	13	# Object file lists
14	14	obj-$(CONFIG_SECURITY) += security.o capability.o

security/commoncap.c+1−1

@@ -1005,7 +1005,7 @@ int cap_file_mmap(struct file *file, unsigned long reqprot, · 1004 unmodified lines
1005	1005	{
1006	1006	int ret = 0;
1007	1007
1008		− if (addr < mmap_min_addr) {
	1008	+ if (addr < dac_mmap_min_addr) {
1009	1009	ret = cap_capable(current, current_cred(), CAP_SYS_RAWIO,
1010	1010	SECURITY_CAP_AUDIT);
1011	1011	/* set PF_SUPERPRIV if it turns out we allow the low mmap */

security/min_addr.c+49−0

@@ -0,0 +1,49 @@
	1	+#include <linux/init.h>
	2	+#include <linux/mm.h>
	3	+#include <linux/security.h>
	4	+#include <linux/sysctl.h>
	5	+
	6	+/* amount of vm to protect from userspace access by both DAC and the LSM*/
	7	+unsigned long mmap_min_addr;
	8	+/* amount of vm to protect from userspace using CAP_SYS_RAWIO (DAC) */
	9	+unsigned long dac_mmap_min_addr = CONFIG_DEFAULT_MMAP_MIN_ADDR;
	10	+/* amount of vm to protect from userspace using the LSM = CONFIG_LSM_MMAP_MIN_ADDR */
	11	+
	12	+/*
	13	+ * Update mmap_min_addr = max(dac_mmap_min_addr, CONFIG_LSM_MMAP_MIN_ADDR)
	14	+ */
	15	+static void update_mmap_min_addr(void)
	16	+{
	17	+#ifdef CONFIG_LSM_MMAP_MIN_ADDR
	18	+ if (dac_mmap_min_addr > CONFIG_LSM_MMAP_MIN_ADDR)
	19	+ mmap_min_addr = dac_mmap_min_addr;
	20	+ else
	21	+ mmap_min_addr = CONFIG_LSM_MMAP_MIN_ADDR;
	22	+#else
	23	+ mmap_min_addr = dac_mmap_min_addr;
	24	+#endif
	25	+}
	26	+
	27	+/*
	28	+ * sysctl handler which just sets dac_mmap_min_addr = the new value and then
	29	+ * calls update_mmap_min_addr() so non MAP_FIXED hints get rounded properly
	30	+ */
	31	+int mmap_min_addr_handler(struct ctl_table table, int write, struct file filp,
	32	+ void __user buffer, size_t lenp, loff_t *ppos)
	33	+{
	34	+ int ret;
	35	+
	36	+ ret = proc_doulongvec_minmax(table, write, filp, buffer, lenp, ppos);
	37	+
	38	+ update_mmap_min_addr();
	39	+
	40	+ return ret;
	41	+}
	42	+
	43	+int __init init_mmap_min_addr(void)
	44	+{
	45	+ update_mmap_min_addr();
	46	+
	47	+ return 0;
	48	+}
	49	+pure_initcall(init_mmap_min_addr);

security/selinux/hooks.c+1−1

@@ -3036,7 +3036,7 @@ static int selinux_file_mmap(struct file *file, unsigned long reqprot, · 3035 unmodified lines
3036	3036	* at bad behaviour/exploit that we always want to get the AVC, even
3037	3037	* if DAC would have also denied the operation.
3038	3038	*/
3039		− if (addr < mmap_min_addr) {
	3039	+ if (addr < CONFIG_LSM_MMAP_MIN_ADDR) {
3040	3040	rc = avc_has_perm(sid, sid, SECCLASS_MEMPROTECT,
3041	3041	MEMPROTECT__MMAP_ZERO, NULL);
3042	3042	if (rc)