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PM / hibernate: Image data protection during restoration

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Make it possible to protect all pages holding image data during
hibernate image restoration by setting them read-only (so as to
catch attempts to write to those pages after image data have been
stored in them).

This adds overhead to image restoration code (it may cause large
page mappings to be split as a result of page flags changes) and
the errors it protects against should never happen in theory, so
the feature is only active after passing hibernate=protect_image
to the command line of the restore kernel.

Also it only is built if CONFIG_DEBUG_RODATA is set.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Rafael J. Wysocki 2016-07-10 02:12:10 +02:00
parent d5f32af310
commit 4c0b6c10fb
4 changed files with 55 additions and 0 deletions
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3
Documentation/kernel-parameters.txt
View File

@ -3594,6 +3594,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
present during boot.
nocompress Don't compress/decompress hibernation images.
no Disable hibernation and resume.
protect_image Turn on image protection during restoration
(that will set all pages holding image data
during restoration read-only).
retain_initrd [RAM] Keep initrd memory after extraction

3
kernel/power/hibernate.c
View File

@ -1126,6 +1126,9 @@ static int __init hibernate_setup(char *str)
} else if (!strncmp(str, "no", 2)) {
noresume = 1;
nohibernate = 1;
} else if (IS_ENABLED(CONFIG_DEBUG_RODATA)
&& !strncmp(str, "protect_image", 13)) {
enable_restore_image_protection();
}
return 1;
}

7
kernel/power/power.h
View File

@ -59,6 +59,13 @@ extern int hibernation_snapshot(int platform_mode);
extern int hibernation_restore(int platform_mode);
extern int hibernation_platform_enter(void);
#ifdef CONFIG_DEBUG_RODATA
/* kernel/power/snapshot.c */
extern void enable_restore_image_protection(void);
#else
static inline void enable_restore_image_protection(void) {}
#endif /* CONFIG_DEBUG_RODATA */
#else /* !CONFIG_HIBERNATION */
static inline void hibernate_reserved_size_init(void) {}

42
kernel/power/snapshot.c
View File

@ -38,6 +38,43 @@
#include "power.h"
#ifdef CONFIG_DEBUG_RODATA
static bool hibernate_restore_protection;
static bool hibernate_restore_protection_active;
void enable_restore_image_protection(void)
{
hibernate_restore_protection = true;
}
static inline void hibernate_restore_protection_begin(void)
{
hibernate_restore_protection_active = hibernate_restore_protection;
}
static inline void hibernate_restore_protection_end(void)
{
hibernate_restore_protection_active = false;
}
static inline void hibernate_restore_protect_page(void *page_address)
{
if (hibernate_restore_protection_active)
set_memory_ro((unsigned long)page_address, 1);
}
static inline void hibernate_restore_unprotect_page(void *page_address)
{
if (hibernate_restore_protection_active)
set_memory_rw((unsigned long)page_address, 1);
}
#else
static inline void hibernate_restore_protection_begin(void) {}
static inline void hibernate_restore_protection_end(void) {}
static inline void hibernate_restore_protect_page(void *page_address) {}
static inline void hibernate_restore_unprotect_page(void *page_address) {}
#endif /* CONFIG_DEBUG_RODATA */
static int swsusp_page_is_free(struct page *);
static void swsusp_set_page_forbidden(struct page *);
static void swsusp_unset_page_forbidden(struct page *);
@ -1414,6 +1451,7 @@ loop:
memory_bm_clear_current(forbidden_pages_map);
memory_bm_clear_current(free_pages_map);
hibernate_restore_unprotect_page(page_address(page));
__free_page(page);
goto loop;
}
@ -1425,6 +1463,7 @@ out:
buffer = NULL;
alloc_normal = 0;
alloc_highmem = 0;
hibernate_restore_protection_end();
}
/* Helper functions used for the shrinking of memory. */
@ -2548,6 +2587,7 @@ int snapshot_write_next(struct snapshot_handle *handle)
if (error)
return error;
hibernate_restore_protection_begin();
} else if (handle->cur <= nr_meta_pages + 1) {
error = unpack_orig_pfns(buffer, &copy_bm);
if (error)
@ -2570,6 +2610,7 @@ int snapshot_write_next(struct snapshot_handle *handle)
copy_last_highmem_page();
/* Restore page key for data page (s390 only). */
page_key_write(handle->buffer);
hibernate_restore_protect_page(handle->buffer);
handle->buffer = get_buffer(&orig_bm, &ca);
if (IS_ERR(handle->buffer))
return PTR_ERR(handle->buffer);
@ -2594,6 +2635,7 @@ void snapshot_write_finalize(struct snapshot_handle *handle)
/* Restore page key for data page (s390 only). */
page_key_write(handle->buffer);
page_key_free();
hibernate_restore_protect_page(handle->buffer);
/* Do that only if we have loaded the image entirely */
if (handle->cur > 1 && handle->cur > nr_meta_pages + nr_copy_pages) {
memory_bm_recycle(&orig_bm);