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rafaeljwrafaeljw
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PM / hibernate: Image data protection during restoration
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>
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‎Documentation/kernel-parameters.txt

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Original file line numberDiff line numberDiff line change
@@ -3594,6 +3594,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
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present during boot.
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nocompress Don't compress/decompress hibernation images.
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no Disable hibernation and resume.
3597+
protect_image Turn on image protection during restoration
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(that will set all pages holding image data
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during restoration read-only).
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retain_initrd [RAM] Keep initrd memory after extraction
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‎kernel/power/hibernate.c

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@@ -1126,6 +1126,9 @@ static int __init hibernate_setup(char *str)
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} else if (!strncmp(str, "no", 2)) {
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noresume = 1;
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nohibernate = 1;
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} else if (IS_ENABLED(CONFIG_DEBUG_RODATA)
1130+
&& !strncmp(str, "protect_image", 13)) {
1131+
enable_restore_image_protection();
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}
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return 1;
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}

‎kernel/power/power.h

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -59,6 +59,13 @@ extern int hibernation_snapshot(int platform_mode);
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extern int hibernation_restore(int platform_mode);
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extern int hibernation_platform_enter(void);
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#ifdef CONFIG_DEBUG_RODATA
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/* kernel/power/snapshot.c */
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extern void enable_restore_image_protection(void);
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#else
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static inline void enable_restore_image_protection(void) {}
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#endif /* CONFIG_DEBUG_RODATA */
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6269
#else /* !CONFIG_HIBERNATION */
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static inline void hibernate_reserved_size_init(void) {}

‎kernel/power/snapshot.c

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Original file line numberDiff line numberDiff line change
@@ -38,6 +38,43 @@
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#include "power.h"
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#ifdef CONFIG_DEBUG_RODATA
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static bool hibernate_restore_protection;
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static bool hibernate_restore_protection_active;
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void enable_restore_image_protection(void)
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{
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hibernate_restore_protection = true;
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}
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static inline void hibernate_restore_protection_begin(void)
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{
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hibernate_restore_protection_active = hibernate_restore_protection;
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}
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static inline void hibernate_restore_protection_end(void)
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{
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hibernate_restore_protection_active = false;
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}
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static inline void hibernate_restore_protect_page(void *page_address)
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{
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if (hibernate_restore_protection_active)
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set_memory_ro((unsigned long)page_address, 1);
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}
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static inline void hibernate_restore_unprotect_page(void *page_address)
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{
68+
if (hibernate_restore_protection_active)
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set_memory_rw((unsigned long)page_address, 1);
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}
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#else
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static inline void hibernate_restore_protection_begin(void) {}
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static inline void hibernate_restore_protection_end(void) {}
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static inline void hibernate_restore_protect_page(void *page_address) {}
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static inline void hibernate_restore_unprotect_page(void *page_address) {}
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#endif /* CONFIG_DEBUG_RODATA */
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static int swsusp_page_is_free(struct page *);
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static void swsusp_set_page_forbidden(struct page *);
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static void swsusp_unset_page_forbidden(struct page *);
@@ -1414,6 +1451,7 @@ void swsusp_free(void)
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memory_bm_clear_current(forbidden_pages_map);
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memory_bm_clear_current(free_pages_map);
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hibernate_restore_unprotect_page(page_address(page));
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__free_page(page);
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goto loop;
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}
@@ -1425,6 +1463,7 @@ void swsusp_free(void)
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buffer = NULL;
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alloc_normal = 0;
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alloc_highmem = 0;
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hibernate_restore_protection_end();
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}
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/* Helper functions used for the shrinking of memory. */
@@ -2548,6 +2587,7 @@ int snapshot_write_next(struct snapshot_handle *handle)
25482587
if (error)
25492588
return error;
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hibernate_restore_protection_begin();
25512591
} else if (handle->cur <= nr_meta_pages + 1) {
25522592
error = unpack_orig_pfns(buffer, &copy_bm);
25532593
if (error)
@@ -2570,6 +2610,7 @@ int snapshot_write_next(struct snapshot_handle *handle)
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copy_last_highmem_page();
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/* Restore page key for data page (s390 only). */
25722612
page_key_write(handle->buffer);
2613+
hibernate_restore_protect_page(handle->buffer);
25732614
handle->buffer = get_buffer(&orig_bm, &ca);
25742615
if (IS_ERR(handle->buffer))
25752616
return PTR_ERR(handle->buffer);
@@ -2594,6 +2635,7 @@ void snapshot_write_finalize(struct snapshot_handle *handle)
25942635
/* Restore page key for data page (s390 only). */
25952636
page_key_write(handle->buffer);
25962637
page_key_free();
2638+
hibernate_restore_protect_page(handle->buffer);
25972639
/* Do that only if we have loaded the image entirely */
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if (handle->cur > 1 && handle->cur > nr_meta_pages + nr_copy_pages) {
25992641
memory_bm_recycle(&orig_bm);

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