Messages in this thread | | | From | Brian Geffon <> | Date | Tue, 3 Oct 2023 10:33:38 -0400 | Subject | Re: [PATCH] PM: hibernate: Fix a bug in copying the zero bitmap to safe pages |
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On Mon, Oct 2, 2023 at 11:08 PM Pavan Kondeti <quic_pkondeti@quicinc.com> wrote: > > On Sat, Sep 30, 2023 at 07:37:13AM -0400, Brian Geffon wrote: > > On Fri, Sep 29, 2023 at 1:31 PM Pavankumar Kondeti > > <quic_pkondeti@quicinc.com> wrote: > > > > > Hi Pavankumar, > > > > > 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 in prepare_image() > > > to make a copy of zero bitmap after the unsafe pages are marked. > > > Freeing this temporary bitmap 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. > > > > Rafael pulled https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git/commit/?h=linux-next&id=f0c7183008b41e92fa676406d87f18773724b48b > > which addresses the null pointer dereference which regardless > > shouldn't be touching the list directly and should be using > > __get_safe_page(). > > Thanks for pointing me to this. I have verified hibernation by pulling this > commit to v6.6-rc3 and it works as expected. > > This commit is currently queued for v6.7, can it be included in next -rc or > we have to apply the patch I have sent to make sure that hibernation works on > v6.6 when it gets released.
It was CCed to stable, so it will be included in stable kernels.
> > > > > > > > > Fixes: 005e8dddd497 ("PM: hibernate: don't store zero pages in the image file") > > > Signed-off-by: Pavankumar Kondeti <quic_pkondeti@quicinc.com> > > Thanks, > Pavan
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