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module: Rework layout alignment to avoid BUG_ON()s

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

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
This commit is contained in:
Christophe Leroy 2022-02-23 10:01:00 +01:00 committed by Luis Chamberlain
parent 32a08c17d8
commit ef505058dc
3 changed files with 24 additions and 9 deletions
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1
kernel/module/internal.h
View file

@ -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);

5
kernel/module/main.c
View file

@ -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;

27
kernel/module/strict_rwx.c
View file

@ -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) ||