Commit b33465fe authored by Aaron Tomlin's avatar Aaron Tomlin Committed by Luis Chamberlain
Browse files

module: Move strict rwx support to a separate file 



No functional change.

This patch migrates code that makes module text
and rodata memory read-only and non-text memory
non-executable from core module code into
kernel/module/strict_rwx.c.

Reviewed-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarAaron Tomlin <atomlin@redhat.com>
Signed-off-by: default avatarLuis Chamberlain <mcgrof@kernel.org>
parent 58d208de

kernel/module/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -12,3 +12,4 @@ obj-$(CONFIG_MODULE_DECOMPRESS) += decompress.o 
obj-$(CONFIG_MODULE_SIG) += signing.o

obj-$(CONFIG_LIVEPATCH) += livepatch.o

obj-$(CONFIG_MODULES_TREE_LOOKUP) += tree_lookup.o

obj-$(CONFIG_STRICT_MODULE_RWX) += strict_rwx.o

kernel/module/internal.h

+32 −0
Original line number Diff line number Diff line
@@ -20,6 +20,17 @@ 
/* Maximum number of characters written by module_flags() */

#define MODULE_FLAGS_BUF_SIZE (TAINT_FLAGS_COUNT + 4)



/*

 * Modules' sections will be aligned on page boundaries

 * to ensure complete separation of code and data, but

 * only when CONFIG_ARCH_HAS_STRICT_MODULE_RWX=y

 */

#ifdef CONFIG_ARCH_HAS_STRICT_MODULE_RWX

# define debug_align(X) PAGE_ALIGN(X)

#else

# define debug_align(X) (X)

#endif



extern struct mutex module_mutex;

extern struct list_head modules;
@@ -126,3 +137,24 @@ static inline struct module *mod_find(unsigned long addr) 
	return NULL;

}

#endif /* CONFIG_MODULES_TREE_LOOKUP */



#ifdef CONFIG_ARCH_HAS_STRICT_MODULE_RWX

void frob_text(const struct module_layout *layout, int (*set_memory)(unsigned long start,

								     int num_pages));

#endif /* CONFIG_ARCH_HAS_STRICT_MODULE_RWX */



#ifdef CONFIG_STRICT_MODULE_RWX

void module_enable_ro(const struct module *mod, bool after_init);

void module_enable_nx(const struct module *mod);

int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,

				char *secstrings, struct module *mod);



#else /* !CONFIG_STRICT_MODULE_RWX */

static inline void module_enable_nx(const struct module *mod) { }

static inline void module_enable_ro(const struct module *mod, bool after_init) {}

static inline int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,

				       char *secstrings, struct module *mod)

{

	return 0;

}

#endif /* CONFIG_STRICT_MODULE_RWX */

kernel/module/main.c

+2 −97
Original line number Diff line number Diff line
@@ -63,17 +63,6 @@ 
#define CREATE_TRACE_POINTS

#include <trace/events/module.h>



/*

 * Modules' sections will be aligned on page boundaries

 * to ensure complete separation of code and data, but

 * only when CONFIG_ARCH_HAS_STRICT_MODULE_RWX=y

 */

#ifdef CONFIG_ARCH_HAS_STRICT_MODULE_RWX

# define debug_align(X) ALIGN(X, PAGE_SIZE)

#else

# define debug_align(X) (X)

#endif



/*

 * Mutex protects:

 * 1) List of modules (also safely readable with preempt_disable),
@@ -1819,7 +1808,7 @@ static void mod_sysfs_teardown(struct module *mod) 
 * whether we are strict.

 */

#ifdef CONFIG_ARCH_HAS_STRICT_MODULE_RWX

static void frob_text(const struct module_layout *layout,

void frob_text(const struct module_layout *layout,

	       int (*set_memory)(unsigned long start, int num_pages))

{

	BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
@@ -1837,90 +1826,6 @@ static void module_enable_x(const struct module *mod) 
static void module_enable_x(const struct module *mod) { }

#endif /* CONFIG_ARCH_HAS_STRICT_MODULE_RWX */



#ifdef CONFIG_STRICT_MODULE_RWX

static void frob_rodata(const struct module_layout *layout,

			int (*set_memory)(unsigned long start, int num_pages))

{

	BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));

	BUG_ON((unsigned long)layout->text_size & (PAGE_SIZE-1));

	BUG_ON((unsigned long)layout->ro_size & (PAGE_SIZE-1));

	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))

{

	BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));

	BUG_ON((unsigned long)layout->ro_size & (PAGE_SIZE-1));

	BUG_ON((unsigned long)layout->ro_after_init_size & (PAGE_SIZE-1));

	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))

{

	BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));

	BUG_ON((unsigned long)layout->ro_after_init_size & (PAGE_SIZE-1));

	BUG_ON((unsigned long)layout->size & (PAGE_SIZE-1));

	set_memory((unsigned long)layout->base + layout->ro_after_init_size,

		   (layout->size - layout->ro_after_init_size) >> PAGE_SHIFT);

}



static void module_enable_ro(const struct module *mod, bool after_init)

{

	if (!rodata_enabled)

		return;



	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->core_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->core_layout, set_memory_ro);

}



static void module_enable_nx(const struct module *mod)

{

	frob_rodata(&mod->core_layout, set_memory_nx);

	frob_ro_after_init(&mod->core_layout, set_memory_nx);

	frob_writable_data(&mod->core_layout, set_memory_nx);

	frob_rodata(&mod->init_layout, set_memory_nx);

	frob_writable_data(&mod->init_layout, set_memory_nx);

}



static 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;



	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;

}



#else /* !CONFIG_STRICT_MODULE_RWX */

static void module_enable_nx(const struct module *mod) { }

static void module_enable_ro(const struct module *mod, bool after_init) {}

static int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,

				       char *secstrings, struct module *mod)

{

	return 0;

}

#endif /*  CONFIG_STRICT_MODULE_RWX */



void __weak module_memfree(void *module_region)

{

	/*

kernel/module/strict_rwx.c

0 → 100644
+85 −0
Original line number Diff line number Diff line 
// 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"



static void frob_rodata(const struct module_layout *layout,

		 int (*set_memory)(unsigned long start, int num_pages))

{

	BUG_ON(!PAGE_ALIGNED(layout->base));

	BUG_ON(!PAGE_ALIGNED(layout->text_size));

	BUG_ON(!PAGE_ALIGNED(layout->ro_size));

	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))

{

	BUG_ON(!PAGE_ALIGNED(layout->base));

	BUG_ON(!PAGE_ALIGNED(layout->ro_size));

	BUG_ON(!PAGE_ALIGNED(layout->ro_after_init_size));

	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))

{

	BUG_ON(!PAGE_ALIGNED(layout->base));

	BUG_ON(!PAGE_ALIGNED(layout->ro_after_init_size));

	BUG_ON(!PAGE_ALIGNED(layout->size));

	set_memory((unsigned long)layout->base + layout->ro_after_init_size,

		   (layout->size - layout->ro_after_init_size) >> PAGE_SHIFT);

}



void module_enable_ro(const struct module *mod, bool after_init)

{

	if (!rodata_enabled)

		return;



	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->core_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->core_layout, set_memory_ro);

}



void module_enable_nx(const struct module *mod)

{

	frob_rodata(&mod->core_layout, set_memory_nx);

	frob_ro_after_init(&mod->core_layout, set_memory_nx);

	frob_writable_data(&mod->core_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;



	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;

}