Re: Speculative page faults

[Laurent Dufour <ldufour@linux.ibm.com>]

Le 08/09/2019 à 10:31, zhong jiang a écrit :
> Hi, Laurent,  Vinayak
> 
> I have got the following crash on 4.14 kernel with speculative page faults enabled.
> Unfortunately,  The issue disappears when trying disabling SPF.

Hi Zhong,

Sorry for to late answer, I was busy at the LPC.

I never hit that.

Is there any steps identified leading to this crash ?

Thanks,
Laurent.


> The call trace is as follows.
> 
> Unable to handle kernel NULL pointer dereference at virtual address 00000000
> user pgtable: 4k pages, 39-bit VAs, pgd = ffffffc177337000
> [0000000000000000] *pgd=0000000177346003, *pud=0000000177346003, *pmd=0000000000000000
> Internal error: Oops: 96000046 [#1] PREEMPT SMP
> 
> CPU: 0 PID: 3184 Comm: Signal Catcher VIP: 00 Tainted: G           O    4.14.116 #1
> PC is at __rb_erase_color+0x54/0x260
> LR is at anon_vma_interval_tree_remove+0x2ac/0x2c0
> 
> Call trace:
> [<ffffff8009aa45c4>] __rb_erase_color+0x54/0x260
> [<ffffff80083a73f8>] anon_vma_interval_tree_remove+0x2ac/0x2c0
> [<ffffff80083b96ac>] unlink_anon_vmas+0x84/0x170
> [<ffffff80083aa8f4>] free_pgtables+0x9c/0x100
> [<ffffff80083b6814>] exit_mmap+0xb0/0x1d8
> [<ffffff8008227e8c>] mmput+0x3c/0xe0
> [ffffff800822ed00>] do_exit+0x2f0/0x954
> [<ffffff800822f41c>] do_group_exit+0x88/0x9c
> [<ffffff800823b768>] get_signal+0x360/0x56c
> [<ffffff8008208eb8>] do_notify_resume+0x150/0x5e4
> Exception stack(0xffffffc1eac07ec0 to 0xffffffc1eac08000)
> 
> It seems to rb_node is empty accidentally under anon_vma rwsem when the process is exiting.
> I have no idea whether any race existence or not to result in the issue.
> 
> Let me know if you have hit the issue or any  suggestions.
> 
> Thanks,
> zhong jiang
>