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