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Pavankumar Kondeti authored
The following crash is observed 100% of the time during resume from the hibernation on a x86 QEMU system. [ 12.931887] ? __die_body+0x1a/0x60 [ 12.932324] ? page_fault_oops+0x156/0x420 [ 12.932824] ? search_exception_tables+0x37/0x50 [ 12.933389] ? fixup_exception+0x21/0x300 [ 12.933889] ? exc_page_fault+0x69/0x150 [ 12.934371] ? asm_exc_page_fault+0x26/0x30 [ 12.934869] ? get_buffer.constprop.0+0xac/0x100 [ 12.935428] snapshot_write_next+0x7c/0x9f0 [ 12.935929] ? submit_bio_noacct_nocheck+0x2c2/0x370 [ 12.936530] ? submit_bio_noacct+0x44/0x2c0 [ 12.937035] ? hib_submit_io+0xa5/0x110 [ 12.937501] load_image+0x83/0x1a0 [ 12.937919] swsusp_read+0x17f/0x1d0 [ 12.938355] ? create_basic_memory_bitmaps+0x1b7/0x240 [ 12.938967] load_image_and_restore+0x45/0xc0 [ 12.939494] software_resume+0x13c/0x180 [ 12.939994] resume_store+0xa3/0x1d0 The commit being fixed introduced a bug in copying the zero bitmap to safe pages. A temporary bitmap is allocated with PG_ANY flag in prepare_image() to make a copy of zero bitmap after the unsafe pages are marked. Freeing this temporary bitmap with PG_UNSAFE_KEEP later results in an inconsistent state of unsafe pages. Since free bit is left as is for this temporary bitmap after free, these pages are treated as unsafe pages when they are allocated again. This results in incorrect calculation of the number of pages pre-allocated for the image. nr_pages = (nr_zero_pages + nr_copy_pages) - nr_highmem - allocated_unsafe_pages; The allocate_unsafe_pages is estimated to be higher than the actual which results in running short of pages in safe_pages_list. Hence the crash is observed in get_buffer() due to NULL pointer access of safe_pages_list. Fix this issue by creating the temporary zero bitmap from safe pages (free bit not set) so that the corresponding free bits can be cleared while freeing this bitmap. Fixes: 005e8ddd ("PM: hibernate: don't store zero pages in the image file") Suggested-by: : Brian Geffon <bgeffon@google.com> Signed-off-by: Pavankumar Kondeti <quic_pkondeti@quicinc.com> Reviewed-by: Brian Geffon <bgeffon@google.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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