1 files changed, 53 insertions, 0 deletions
diff --git a/security/min_addr.c b/security/min_addr.c
new file mode 100644
index 000000000..94d2b0cf0
--- /dev/null
+++ b/security/min_addr.c
@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0
+#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,
+			  void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	int ret;
+
+	if (write && !capable(CAP_SYS_RAWIO))
+		return -EPERM;
+
+	ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
+
+	update_mmap_min_addr();
+
+	return ret;
+}
+
+static int __init init_mmap_min_addr(void)
+{
+	update_mmap_min_addr();
+
+	return 0;
+}
+pure_initcall(init_mmap_min_addr);