Commit ef505058 authored by Christophe Leroy's avatar Christophe Leroy Committed by Luis Chamberlain
Browse files

module: Rework layout alignment to avoid BUG_ON()s 



Perform layout alignment verification up front and WARN_ON()
and fail module loading instead of crashing the machine.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarLuis Chamberlain <mcgrof@kernel.org>
parent 32a08c17

kernel/module/internal.h

+1 −0
Original line number Diff line number Diff line
@@ -180,6 +180,7 @@ void module_enable_nx(const struct module *mod); 
void module_enable_x(const struct module *mod);

int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,

				char *secstrings, struct module *mod);

bool module_check_misalignment(const struct module *mod);



#ifdef CONFIG_MODULE_SIG

int module_sig_check(struct load_info *info, int flags);

kernel/module/main.c

+5 −0
Original line number Diff line number Diff line
@@ -2550,6 +2550,9 @@ static int complete_formation(struct module *mod, struct load_info *info) 
	/* This relies on module_mutex for list integrity. */

	module_bug_finalize(info->hdr, info->sechdrs, mod);



	if (module_check_misalignment(mod))

		goto out_misaligned;



	module_enable_ro(mod, false);

	module_enable_nx(mod);

	module_enable_x(mod);
@@ -2563,6 +2566,8 @@ static int complete_formation(struct module *mod, struct load_info *info) 


	return 0;



out_misaligned:

	err = -EINVAL;

out:

	mutex_unlock(&module_mutex);

	return err;

kernel/module/strict_rwx.c

+18 −9
Original line number Diff line number Diff line
@@ -42,9 +42,6 @@ static void frob_text(const struct module_layout *layout, 
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);

}
@@ -52,9 +49,6 @@ static void frob_rodata(const struct module_layout *layout, 
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);

}
@@ -62,13 +56,28 @@ static void frob_ro_after_init(const struct module_layout *layout, 
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);

}



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->init_layout);

}



void module_enable_x(const struct module *mod)

{

	if (!PAGE_ALIGNED(mod->core_layout.base) ||