Re: BUG: Bad page state in process dirtyc0w_child

Heiko Carstens
2020-09-16T20:37:20Z

On Sat, Sep 12, 2020 at 09:54:12PM -0400, Qian Cai wrote:
> Occasionally, running this LTP test will trigger an error below on
> s390:
> https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/security/dirtyc0w/dirtyc0w.c
> https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/security/dirtyc0w/dirtyc0w_child.c
>
> this .config:
> https://gitlab.com/cailca/linux-mm/-/blob/master/s390.config
>
> [ 6970.253173] LTP: starting dirtyc0w
> [ 6971.599102] BUG: Bad page state in process dirtyc0w_child pfn:8865d
> [ 6971.599867] page:000000001a8328d7 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x8865d
> [ 6971.599876] flags: 0x400000000008000e(referenced|uptodate|dirty|swapbacked)
> [ 6971.599886] raw: 400000000008000e 0000000000000100 0000000000000122 0000000000000000
> [ 6971.599893] raw: 0000000000000000 0000000000000000 ffffffff00000000 0000000000000000
> [ 6971.599900] page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
> [ 6971.599906] Modules linked in: loop kvm ip_tables x_tables dm_mirror dm_region_hash dm_log dm_mod [last unloaded: dummy_del_mod]
> [ 6971.599952] CPU: 1 PID: 65238 Comm: dirtyc0w_child Tainted: G O 5.9.0-rc4-next-20200909 #1
> [ 6971.599959] Hardware name: IBM 2964 N96 400 (z/VM 6.4.0)
> [ 6971.599964] Call Trace:
> [ 6971.599979] [<0000000073aec038>] show_stack+0x158/0x1f0
> [ 6971.599986] [<0000000073af724a>] dump_stack+0x1f2/0x238
> [ 6971.599994] [<0000000072ed086a>] bad_page+0x1ba/0x1c0
> [ 6971.600000] [<0000000072ed20c4>] free_pcp_prepare+0x4fc/0x658
> [ 6971.600006] [<0000000072ed96a6>] free_unref_page+0xae/0x158
> [ 6971.600013] [<0000000072e8286a>] unmap_page_range+0xb62/0x1df8
> [ 6971.600019] [<0000000072e83bbc>] unmap_single_vma+0xbc/0x1c8
> [ 6971.600025] [<0000000072e8418e>] zap_page_range+0x176/0x230
> [ 6971.600033] [<0000000072eece8e>] do_madvise+0xfde/0x1270
> [ 6971.600039] [<0000000072eed50a>] __s390x_sys_madvise+0x72/0x98
> [ 6971.600047] [<0000000073b1cce4>] system_call+0xdc/0x278
> [ 6971.600053] 2 locks held by dirtyc0w_child/65238:
> [ 6971.600058] #0: 000000013442fa18 (&mm->mmap_lock){++++}-{3:3}, at: do_madvise+0x17a/0x1270
> [ 6971.600432] #1: 00000001343f9060 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: unmap_page_range+0x640/0x1df8
> [ 6971.600487] Disabling lock debugging due to kernel taint
>
> Once it happens, running it again will trigger in on another PFN.
>
> [39717.085115] BUG: Bad page state in process dirtyc0w_child pfn:af065
>
> Any thoughts?

Alexander, Gerald, could you take a look?