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![Christophe Leroy](/assets/img/avatar_default.png)
Add CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC to allow architectures to request having modules data in vmalloc area instead of module area. This is required on powerpc book3s/32 in order to set data non executable, because it is not possible to set executability on page basis, this is done per 256 Mbytes segments. The module area has exec right, vmalloc area has noexec. This can also be useful on other powerpc/32 in order to maximize the chance of code being close enough to kernel core to avoid branch trampolines. Cc: Jason Wessel <jason.wessel@windriver.com> Acked-by: Daniel Thompson <daniel.thompson@linaro.org> Cc: Douglas Anderson <dianders@chromium.org> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> [mcgrof: rebased in light of kernel/module/kdb.c move] Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
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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