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module: clean up RO/NX handling.
Modules have three sections: text, rodata and writable data. The code handled the case where these overlapped, however they never can: debug_align() ensures they are always page-aligned. This is why we got away with manually traversing the pages in set_all_modules_text_rw() without rounding. We create three helper functions: frob_text(), frob_rodata() and frob_writable_data(). We then call these explicitly at every point, so it's clear what we're doing. We also expose module_enable_ro() and module_disable_ro() for livepatch to use. Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
This commit is contained in:
Rusty Russell
Jiri Kosina
parent
7523e4dc50
commit
85c898db63
@ -762,9 +762,13 @@ extern int module_sysfs_initialized;
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#ifdef CONFIG_DEBUG_SET_MODULE_RONX
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extern void set_all_modules_text_rw(void);
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extern void set_all_modules_text_ro(void);
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extern void module_enable_ro(const struct module *mod);
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extern void module_disable_ro(const struct module *mod);
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#else
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static inline void set_all_modules_text_rw(void) { }
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static inline void set_all_modules_text_ro(void) { }
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static inline void module_enable_ro(const struct module *mod) { }
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static inline void module_disable_ro(const struct module *mod) { }
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#endif
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#ifdef CONFIG_GENERIC_BUG
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170
kernel/module.c
170
kernel/module.c
@ -80,15 +80,6 @@
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# define debug_align(X) (X)
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#endif
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/*
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* Given BASE and SIZE this macro calculates the number of pages the
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* memory regions occupies
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*/
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#define MOD_NUMBER_OF_PAGES(BASE, SIZE) (((SIZE) > 0) ? \
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(PFN_DOWN((unsigned long)(BASE) + (SIZE) - 1) - \
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PFN_DOWN((unsigned long)BASE) + 1) \
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: (0UL))
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/* If this is set, the section belongs in the init part of the module */
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#define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
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@ -1858,74 +1849,75 @@ static void mod_sysfs_teardown(struct module *mod)
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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] [writable data]
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* text_size -----^ ^ ^
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* ro_size ------------------------| |
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* size -------------------------------------------|
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*
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* These values are always page-aligned (as is base)
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*/
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void set_page_attributes(void *start, void *end, int (*set)(unsigned long start, int num_pages))
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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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unsigned long begin_pfn = PFN_DOWN((unsigned long)start);
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unsigned long end_pfn = PFN_DOWN((unsigned long)end);
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if (end_pfn > begin_pfn)
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set(begin_pfn << PAGE_SHIFT, end_pfn - begin_pfn);
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BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
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BUG_ON((unsigned long)layout->text_size & (PAGE_SIZE-1));
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set_memory((unsigned long)layout->base,
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layout->text_size >> PAGE_SHIFT);
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}
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static void set_section_ro_nx(void *base,
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unsigned long text_size,
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unsigned long ro_size,
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unsigned long total_size,
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int (*set_ro)(unsigned long start, int num_pages),
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int (*set_nx)(unsigned long start, int num_pages))
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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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/* begin and end PFNs of the current subsection */
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unsigned long begin_pfn;
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unsigned long end_pfn;
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/*
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* Set RO for module text and RO-data:
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* - Always protect first page.
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* - Do not protect last partial page.
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*/
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if (ro_size > 0)
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set_page_attributes(base, base + ro_size, set_ro);
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/*
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* Set NX permissions for module data:
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* - Do not protect first partial page.
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* - Always protect last page.
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*/
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if (total_size > text_size) {
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begin_pfn = PFN_UP((unsigned long)base + text_size);
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end_pfn = PFN_UP((unsigned long)base + total_size);
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if (end_pfn > begin_pfn)
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set_nx(begin_pfn << PAGE_SHIFT, end_pfn - begin_pfn);
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}
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BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
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BUG_ON((unsigned long)layout->text_size & (PAGE_SIZE-1));
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BUG_ON((unsigned long)layout->ro_size & (PAGE_SIZE-1));
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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 set_module_core_ro_nx(struct module *mod)
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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_section_ro_nx(mod->core_layout.base, mod->core_layout.text_size,
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mod->core_layout.ro_size, mod->core_layout.size,
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set_memory_ro, set_memory_nx);
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BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
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BUG_ON((unsigned long)layout->ro_size & (PAGE_SIZE-1));
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BUG_ON((unsigned long)layout->size & (PAGE_SIZE-1));
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set_memory((unsigned long)layout->base + layout->ro_size,
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(layout->size - layout->ro_size) >> PAGE_SHIFT);
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}
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static void unset_module_core_ro_nx(struct module *mod)
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/* livepatching wants to disable read-only so it can frob module. */
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void module_disable_ro(const struct module *mod)
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{
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set_section_ro_nx(mod->core_layout.base, mod->core_layout.text_size,
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mod->core_layout.ro_size, mod->core_layout.size,
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set_memory_rw, set_memory_x);
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frob_text(&mod->core_layout, set_memory_rw);
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frob_rodata(&mod->core_layout, set_memory_rw);
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frob_text(&mod->init_layout, set_memory_rw);
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frob_rodata(&mod->init_layout, set_memory_rw);
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}
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static void set_module_init_ro_nx(struct module *mod)
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void module_enable_ro(const struct module *mod)
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{
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set_section_ro_nx(mod->init_layout.base, mod->init_layout.text_size,
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mod->init_layout.ro_size, mod->init_layout.size,
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set_memory_ro, set_memory_nx);
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frob_text(&mod->core_layout, set_memory_ro);
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frob_rodata(&mod->core_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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}
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static void unset_module_init_ro_nx(struct module *mod)
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static void module_enable_nx(const struct module *mod)
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{
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set_section_ro_nx(mod->init_layout.base, mod->init_layout.text_size,
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mod->init_layout.ro_size, mod->init_layout.size,
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set_memory_rw, set_memory_x);
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frob_rodata(&mod->core_layout, set_memory_nx);
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frob_writable_data(&mod->core_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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static void module_disable_nx(const struct module *mod)
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{
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frob_rodata(&mod->core_layout, set_memory_x);
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frob_writable_data(&mod->core_layout, set_memory_x);
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frob_rodata(&mod->init_layout, set_memory_x);
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frob_writable_data(&mod->init_layout, set_memory_x);
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}
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/* Iterate through all modules and set each module's text as RW */
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@ -1937,16 +1929,9 @@ void set_all_modules_text_rw(void)
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list_for_each_entry_rcu(mod, &modules, list) {
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if (mod->state == MODULE_STATE_UNFORMED)
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continue;
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if ((mod->core_layout.base) && (mod->core_layout.text_size)) {
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set_page_attributes(mod->core_layout.base,
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mod->core_layout.base + mod->core_layout.text_size,
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set_memory_rw);
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}
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if ((mod->init_layout.base) && (mod->init_layout.text_size)) {
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set_page_attributes(mod->init_layout.base,
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mod->init_layout.base + mod->init_layout.text_size,
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set_memory_rw);
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}
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frob_text(&mod->core_layout, set_memory_rw);
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frob_text(&mod->init_layout, set_memory_rw);
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}
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mutex_unlock(&module_mutex);
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}
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@ -1960,24 +1945,25 @@ void set_all_modules_text_ro(void)
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list_for_each_entry_rcu(mod, &modules, list) {
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if (mod->state == MODULE_STATE_UNFORMED)
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continue;
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if ((mod->core_layout.base) && (mod->core_layout.text_size)) {
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set_page_attributes(mod->core_layout.base,
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mod->core_layout.base + mod->core_layout.text_size,
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set_memory_ro);
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}
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if ((mod->init_layout.base) && (mod->init_layout.text_size)) {
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set_page_attributes(mod->init_layout.base,
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mod->init_layout.base + mod->init_layout.text_size,
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set_memory_ro);
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}
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frob_text(&mod->core_layout, set_memory_ro);
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frob_text(&mod->init_layout, set_memory_ro);
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}
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mutex_unlock(&module_mutex);
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}
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static void disable_ro_nx(const struct module_layout *layout)
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{
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frob_text(layout, set_memory_rw);
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frob_rodata(layout, set_memory_rw);
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frob_rodata(layout, set_memory_x);
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frob_writable_data(layout, set_memory_x);
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}
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#else
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static void set_module_core_ro_nx(struct module *mod) { }
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static void set_module_init_ro_nx(struct module *mod) { }
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static void unset_module_core_ro_nx(struct module *mod) { }
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static void unset_module_init_ro_nx(struct module *mod) { }
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static void disable_ro_nx(const struct module_layout *layout) { }
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static void module_enable_nx(const struct module *mod) { }
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static void module_disable_nx(const struct module *mod) { }
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#endif
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void __weak module_memfree(void *module_region)
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@ -2029,8 +2015,8 @@ static void free_module(struct module *mod)
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synchronize_sched();
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mutex_unlock(&module_mutex);
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/* This may be NULL, but that's OK */
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unset_module_init_ro_nx(mod);
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/* This may be empty, but that's OK */
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disable_ro_nx(&mod->init_layout);
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module_arch_freeing_init(mod);
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module_memfree(mod->init_layout.base);
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kfree(mod->args);
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@ -2040,7 +2026,7 @@ static void free_module(struct module *mod)
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lockdep_free_key_range(mod->core_layout.base, mod->core_layout.size);
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/* Finally, free the core (containing the module structure) */
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unset_module_core_ro_nx(mod);
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disable_ro_nx(&mod->core_layout);
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module_memfree(mod->core_layout.base);
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#ifdef CONFIG_MPU
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@ -3275,7 +3261,7 @@ static noinline int do_init_module(struct module *mod)
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mod->strtab = mod->core_strtab;
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#endif
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mod_tree_remove_init(mod);
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unset_module_init_ro_nx(mod);
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disable_ro_nx(&mod->init_layout);
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module_arch_freeing_init(mod);
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mod->init_layout.base = NULL;
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mod->init_layout.size = 0;
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@ -3370,8 +3356,8 @@ static int complete_formation(struct module *mod, struct load_info *info)
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module_bug_finalize(info->hdr, info->sechdrs, mod);
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/* Set RO and NX regions */
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set_module_init_ro_nx(mod);
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set_module_core_ro_nx(mod);
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module_enable_ro(mod);
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module_enable_nx(mod);
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/* Mark state as coming so strong_try_module_get() ignores us,
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* but kallsyms etc. can see us. */
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@ -3536,8 +3522,8 @@ static int load_module(struct load_info *info, const char __user *uargs,
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MODULE_STATE_GOING, mod);
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/* we can't deallocate the module until we clear memory protection */
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unset_module_init_ro_nx(mod);
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unset_module_core_ro_nx(mod);
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module_disable_ro(mod);
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module_disable_nx(mod);
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ddebug_cleanup:
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dynamic_debug_remove(info->debug);
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