5 files changed, 210 insertions, 1 deletions

diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index 1f7c2491d3dc..e390e31bb4bf 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -191,5 +191,26 @@ static inline int security_netlbl_sid_to_secattr(u32 sid,
 
 const char *security_get_initial_sid_context(u32 sid);
 
+/*
+ * status notifier using mmap interface
+ */
+extern struct page *selinux_kernel_status_page(void);
+
+#define SELINUX_KERNEL_STATUS_VERSION   1
+struct selinux_kernel_status
+{
+        u32     version;        /* version number of thie structure */
+        u32     sequence;       /* sequence number of seqlock logic */
+        u32     enforcing;      /* current setting of enforcing mode */
+        u32     policyload;     /* times of policy reloaded */
+        u32     deny_unknown;   /* current setting of deny_unknown */
+        /*
+         * The version > 0 supports above members.
+         */
+} __attribute__((packed));
+
+extern void selinux_status_update_setenforce(int enforcing);
+extern void selinux_status_update_policyload(int seqno);
+
 #endif /* _SELINUX_SECURITY_H_ */
 
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 79a1bb635662..a2e7a8563b38 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -110,6 +110,7 @@ enum sel_inos {
         SEL_COMPAT_NET, /* whether to use old compat network packet controls */
         SEL_REJECT_UNKNOWN, /* export unknown reject handling to userspace */
         SEL_DENY_UNKNOWN, /* export unknown deny handling to userspace */
+        SEL_STATUS,     /* export current status using mmap() */
         SEL_INO_NEXT,   /* The next inode number to use */
 };
 
@@ -171,6 +172,7 @@ static ssize_t sel_write_enforce(struct file *file, const char __user *buf,
                 if (selinux_enforcing)
                         avc_ss_reset(0);
                 selnl_notify_setenforce(selinux_enforcing);
+                selinux_status_update_setenforce(selinux_enforcing);
         }
         length = count;
 out:
@@ -205,6 +207,59 @@ static const struct file_operations sel_handle_unknown_ops = {
         .llseek         = generic_file_llseek,
 };
 
+static int sel_open_handle_status(struct inode *inode, struct file *filp)
+{
+        struct page    *status = selinux_kernel_status_page();
+
+        if (!status)
+                return -ENOMEM;
+
+        filp->private_data = status;
+
+        return 0;
+}
+
+static ssize_t sel_read_handle_status(struct file *filp, char __user *buf,
+                                      size_t count, loff_t *ppos)
+{
+        struct page    *status = filp->private_data;
+
+        BUG_ON(!status);
+
+        return simple_read_from_buffer(buf, count, ppos,
+                                       page_address(status),
+                                       sizeof(struct selinux_kernel_status));
+}
+
+static int sel_mmap_handle_status(struct file *filp,
+                                  struct vm_area_struct *vma)
+{
+        struct page    *status = filp->private_data;
+        unsigned long   size = vma->vm_end - vma->vm_start;
+
+        BUG_ON(!status);
+
+        /* only allows one page from the head */
+        if (vma->vm_pgoff > 0 || size != PAGE_SIZE)
+                return -EIO;
+        /* disallow writable mapping */
+        if (vma->vm_flags & VM_WRITE)
+                return -EPERM;
+        /* disallow mprotect() turns it into writable */
+        vma->vm_flags &= ~VM_MAYWRITE;
+
+        return remap_pfn_range(vma, vma->vm_start,
+                               page_to_pfn(status),
+                               size, vma->vm_page_prot);
+}
+
+static const struct file_operations sel_handle_status_ops = {
+        .open           = sel_open_handle_status,
+        .read           = sel_read_handle_status,
+        .mmap           = sel_mmap_handle_status,
+        .llseek         = generic_file_llseek,
+};
+
 #ifdef CONFIG_SECURITY_SELINUX_DISABLE
 static ssize_t sel_write_disable(struct file *file, const char __user *buf,
                                  size_t count, loff_t *ppos)
@@ -1612,6 +1667,7 @@ static int sel_fill_super(struct super_block *sb, void *data, int silent)
                 [SEL_CHECKREQPROT] = {"checkreqprot", &sel_checkreqprot_ops, S_IRUGO|S_IWUSR},
                 [SEL_REJECT_UNKNOWN] = {"reject_unknown", &sel_handle_unknown_ops, S_IRUGO},
                 [SEL_DENY_UNKNOWN] = {"deny_unknown", &sel_handle_unknown_ops, S_IRUGO},
+                [SEL_STATUS] = {"status", &sel_handle_status_ops, S_IRUGO},
                 /* last one */ {""}
         };
         ret = simple_fill_super(sb, SELINUX_MAGIC, selinux_files);
diff --git a/security/selinux/ss/Makefile b/security/selinux/ss/Makefile
index 15d4e62917de..974e11c7cf54 100644
--- a/security/selinux/ss/Makefile
+++ b/security/selinux/ss/Makefile
@@ -5,5 +5,5 @@
 EXTRA_CFLAGS += -Isecurity/selinux -Isecurity/selinux/include
 obj-y := ss.o
 
-ss-y := ebitmap.o hashtab.o symtab.o sidtab.o avtab.o policydb.o services.o conditional.o mls.o
+ss-y := ebitmap.o hashtab.o symtab.o sidtab.o avtab.o policydb.o services.o conditional.o mls.o status.o
 
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 9ea2feca3cd4..494ff527c174 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -1791,6 +1791,7 @@ int security_load_policy(void *data, size_t len)
                 selinux_complete_init();
                 avc_ss_reset(seqno);
                 selnl_notify_policyload(seqno);
+                selinux_status_update_policyload(seqno);
                 selinux_netlbl_cache_invalidate();
                 selinux_xfrm_notify_policyload();
                 return 0;
@@ -1870,6 +1871,7 @@ int security_load_policy(void *data, size_t len)
 
         avc_ss_reset(seqno);
         selnl_notify_policyload(seqno);
+        selinux_status_update_policyload(seqno);
         selinux_netlbl_cache_invalidate();
         selinux_xfrm_notify_policyload();
 
@@ -2374,6 +2376,7 @@ out:
         if (!rc) {
                 avc_ss_reset(seqno);
                 selnl_notify_policyload(seqno);
+                selinux_status_update_policyload(seqno);
                 selinux_xfrm_notify_policyload();
         }
         return rc;
diff --git a/security/selinux/ss/status.c b/security/selinux/ss/status.c
new file mode 100644
index 000000000000..5d9b225f8568
--- /dev/null
+++ b/security/selinux/ss/status.c
@@ -0,0 +1,129 @@
+/*
+ * mmap based event notifications for SELinux
+ *
+ * Author: KaiGai Kohei <kaigai@ak.jp.nec.com>
+ *
+ * Copyright (C) 2010 NEC corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2,
+ * as published by the Free Software Foundation.
+ */
+#include <linux/kernel.h>
+#include <linux/gfp.h>
+#include <linux/mm.h>
+#include <linux/mutex.h>
+#include "avc.h"
+#include "services.h"
+
+/*
+ * The selinux_status_page shall be exposed to userspace applications
+ * using mmap interface on /selinux/status.
+ * It enables to notify applications a few events that will cause reset
+ * of userspace access vector without context switching.
+ *
+ * The selinux_kernel_status structure on the head of status page is
+ * protected from concurrent accesses using seqlock logic, so userspace
+ * application should reference the status page according to the seqlock
+ * logic.
+ *
+ * Typically, application checks status->sequence at the head of access
+ * control routine. If it is odd-number, kernel is updating the status,
+ * so please wait for a moment. If it is changed from the last sequence
+ * number, it means something happen, so application will reset userspace
+ * avc, if needed.
+ * In most cases, application shall confirm the kernel status is not
+ * changed without any system call invocations.
+ */
+static struct page *selinux_status_page = NULL;
+static DEFINE_MUTEX(selinux_status_lock);
+
+/*
+ * selinux_kernel_status_page
+ *
+ * It returns a reference to selinux_status_page. If the status page is
+ * not allocated yet, it also tries to allocate it at the first time.
+ */
+struct page *selinux_kernel_status_page(void)
+{
+        struct selinux_kernel_status   *status;
+        struct page                    *result = NULL;
+
+        mutex_lock(&selinux_status_lock);
+        if (!selinux_status_page)
+        {
+                selinux_status_page = alloc_page(GFP_KERNEL|__GFP_ZERO);
+                if (selinux_status_page)
+                {
+                        status = page_address(selinux_status_page);
+
+                        status->version = SELINUX_KERNEL_STATUS_VERSION;
+                        status->sequence = 0;
+                        status->enforcing = selinux_enforcing;
+                        /*
+                         * NOTE: the next policyload event shall set
+                         * a positive value on the status->policyload,
+                         * although it may not be 1, but never zero.
+                         * So, application can know it was updated.
+                         */
+                        status->policyload = 0;
+                        status->deny_unknown = !security_get_allow_unknown();
+                }
+        }
+        result = selinux_status_page;
+        mutex_unlock(&selinux_status_lock);
+
+        return result;
+}
+
+/*
+ * selinux_status_update_setenforce
+ *
+ * It updates status of the current enforcing/permissive mode.
+ */
+void selinux_status_update_setenforce(int enforcing)
+{
+        struct selinux_kernel_status   *status;
+
+        mutex_lock(&selinux_status_lock);
+        if (selinux_status_page)
+        {
+                status = page_address(selinux_status_page);
+
+                status->sequence++;
+                smp_wmb();
+
+                status->enforcing = enforcing;
+
+                smp_wmb();
+                status->sequence++;
+        }
+        mutex_unlock(&selinux_status_lock);
+}
+
+/*
+ * selinux_status_update_policyload
+ *
+ * It updates status of the times of policy reloaded, and current
+ * setting of deny_unknown.
+ */
+void selinux_status_update_policyload(int seqno)
+{
+        struct selinux_kernel_status   *status;
+
+        mutex_lock(&selinux_status_lock);
+        if (selinux_status_page)
+        {
+                status = page_address(selinux_status_page);
+
+                status->sequence++;
+                smp_wmb();
+
+                status->policyload = seqno;
+                status->deny_unknown = !security_get_allow_unknown();
+
+                smp_wmb();
+                status->sequence++;
+        }
+        mutex_unlock(&selinux_status_lock);
+}