Messages in this thread | | | Date | Fri, 6 Oct 2023 18:21:48 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH v2] PM: hibernate: Fix a bug in copying the zero bitmap to safe pages |
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Hi Rafael,
On Wed, Oct 04, 2023 at 08:46:56PM +0200, Rafael J. Wysocki wrote: > On Wed, Oct 4, 2023 at 2:19 PM Brian Geffon <bgeffon@google.com> wrote: > > > > On Wed, Oct 4, 2023 at 1:01 AM Pavankumar Kondeti > > <quic_pkondeti@quicinc.com> wrote: > > > > > > 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. > > > > > > Cc: stable <stable@kernel.org> > > > Fixes: 005e8dddd497 ("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> > > Applied as 6.7 material, but without the Cc: stable tag that is (a) > invalid (there should be vger.kernel.org in the host part) and (b) > unnecessary AFAICS.
Just to check, did you mean as v6.6 material?
I'm consistently hitting this on real arm64 hardware with v6.6-rc*.
If this is v6.7 material, are we going to revert 005e8dddd497 for now?
I've tested the above patch atop v6.6-rc3, and it solves the problem for me, so FWIW:
Tested-by: Mark Rutland <mark.rutland@arm.com>
Thanks, Mark.
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