1 files changed, 143 insertions, 0 deletions
diff --git a/kernel/module/strict_rwx.c b/kernel/module/strict_rwx.c
new file mode 100644
index 000000000..14fbea66f
--- /dev/null
+++ b/kernel/module/strict_rwx.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Module strict rwx
+ *
+ * Copyright (C) 2015 Rusty Russell
+ */
+
+#include <linux/module.h>
+#include <linux/mm.h>
+#include <linux/vmalloc.h>
+#include <linux/set_memory.h>
+#include "internal.h"
+
+/*
+ * LKM RO/NX protection: protect module's text/ro-data
+ * from modification and any data from execution.
+ *
+ * General layout of module is:
+ *          [text] [read-only-data] [ro-after-init] [writable data]
+ * text_size -----^                ^               ^               ^
+ * ro_size ------------------------|               |               |
+ * ro_after_init_size -----------------------------|               |
+ * size -----------------------------------------------------------|
+ *
+ * These values are always page-aligned (as is base) when
+ * CONFIG_STRICT_MODULE_RWX is set.
+ */
+
+/*
+ * Since some arches are moving towards PAGE_KERNEL module allocations instead
+ * of PAGE_KERNEL_EXEC, keep frob_text() and module_enable_x() independent of
+ * CONFIG_STRICT_MODULE_RWX because they are needed regardless of whether we
+ * are strict.
+ */
+static void frob_text(const struct module_layout *layout,
+		      int (*set_memory)(unsigned long start, int num_pages))
+{
+	set_memory((unsigned long)layout->base,
+		   PAGE_ALIGN(layout->text_size) >> PAGE_SHIFT);
+}
+
+static void frob_rodata(const struct module_layout *layout,
+		 int (*set_memory)(unsigned long start, int num_pages))
+{
+	set_memory((unsigned long)layout->base + layout->text_size,
+		   (layout->ro_size - layout->text_size) >> PAGE_SHIFT);
+}
+
+static void frob_ro_after_init(const struct module_layout *layout,
+			int (*set_memory)(unsigned long start, int num_pages))
+{
+	set_memory((unsigned long)layout->base + layout->ro_size,
+		   (layout->ro_after_init_size - layout->ro_size) >> PAGE_SHIFT);
+}
+
+static void frob_writable_data(const struct module_layout *layout,
+			int (*set_memory)(unsigned long start, int num_pages))
+{
+	set_memory((unsigned long)layout->base + layout->ro_after_init_size,
+		   (layout->size - layout->ro_after_init_size) >> PAGE_SHIFT);
+}
+
+static bool layout_check_misalignment(const struct module_layout *layout)
+{
+	return WARN_ON(!PAGE_ALIGNED(layout->base)) ||
+	       WARN_ON(!PAGE_ALIGNED(layout->text_size)) ||
+	       WARN_ON(!PAGE_ALIGNED(layout->ro_size)) ||
+	       WARN_ON(!PAGE_ALIGNED(layout->ro_after_init_size)) ||
+	       WARN_ON(!PAGE_ALIGNED(layout->size));
+}
+
+bool module_check_misalignment(const struct module *mod)
+{
+	if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
+		return false;
+
+	return layout_check_misalignment(&mod->core_layout) ||
+	       layout_check_misalignment(&mod->data_layout) ||
+	       layout_check_misalignment(&mod->init_layout);
+}
+
+void module_enable_x(const struct module *mod)
+{
+	if (!PAGE_ALIGNED(mod->core_layout.base) ||
+	    !PAGE_ALIGNED(mod->init_layout.base))
+		return;
+
+	frob_text(&mod->core_layout, set_memory_x);
+	frob_text(&mod->init_layout, set_memory_x);
+}
+
+void module_enable_ro(const struct module *mod, bool after_init)
+{
+	if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
+		return;
+#ifdef CONFIG_STRICT_MODULE_RWX
+	if (!rodata_enabled)
+		return;
+#endif
+
+	set_vm_flush_reset_perms(mod->core_layout.base);
+	set_vm_flush_reset_perms(mod->init_layout.base);
+	frob_text(&mod->core_layout, set_memory_ro);
+
+	frob_rodata(&mod->data_layout, set_memory_ro);
+	frob_text(&mod->init_layout, set_memory_ro);
+	frob_rodata(&mod->init_layout, set_memory_ro);
+
+	if (after_init)
+		frob_ro_after_init(&mod->data_layout, set_memory_ro);
+}
+
+void module_enable_nx(const struct module *mod)
+{
+	if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
+		return;
+
+	frob_rodata(&mod->data_layout, set_memory_nx);
+	frob_ro_after_init(&mod->data_layout, set_memory_nx);
+	frob_writable_data(&mod->data_layout, set_memory_nx);
+	frob_rodata(&mod->init_layout, set_memory_nx);
+	frob_writable_data(&mod->init_layout, set_memory_nx);
+}
+
+int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
+				char *secstrings, struct module *mod)
+{
+	const unsigned long shf_wx = SHF_WRITE | SHF_EXECINSTR;
+	int i;
+
+	if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
+		return 0;
+
+	for (i = 0; i < hdr->e_shnum; i++) {
+		if ((sechdrs[i].sh_flags & shf_wx) == shf_wx) {
+			pr_err("%s: section %s (index %d) has invalid WRITE|EXEC flags\n",
+			       mod->name, secstrings + sechdrs[i].sh_name, i);
+			return -ENOEXEC;
+		}
+	}
+
+	return 0;
+}