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- // 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;
- }
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