Re: general protection fault in transparent_hugepage_enabled

[Vlastimil Babka]

On 1/2/19 11:03 AM, Dmitry Vyukov wrote:
> On Wed, Jan 2, 2019 at 10:47 AM Vlastimil Babka <vbabka@xxxxxxx> wrote:
>>
>> Actually the fix was folded into the patch that caused the bug, and was
>> already sent to and merged by Linus, commit
>> 7635d9cbe8327e131a1d3d8517dc186c2796ce2e
> 
> 
> But the email thread you referenced says that we need:
> 
> @@ -66,6 +66,8 @@ bool transparent_hugepage_enabled(struct vm_area_struct *vma)
>  {
>   if (vma_is_anonymous(vma))
>   return __transparent_hugepage_enabled(vma);
> + if (!vma->vm_file || !vma->vm_file->f_mapping)
> + return false;
>   if (shmem_mapping(vma->vm_file->f_mapping) && shmem_huge_enabled(vma))
>   return __transparent_hugepage_enabled(vma);
> 
> and 7635d9cbe8327e131a1d3d8517dc186c2796ce2e contains:
> 
> +bool transparent_hugepage_enabled(struct vm_area_struct *vma)
> +{
> +       if (vma_is_anonymous(vma))
> +               return __transparent_hugepage_enabled(vma);
> +       if (vma_is_shmem(vma) && shmem_huge_enabled(vma))
> +               return __transparent_hugepage_enabled(vma);
> +
> +       return false;
> +}
> 
> What am I missing?

Ah, the solution with vma_is_shmem() appeared later in the thread:
https://marc.info/?l=linux-mm&m=154567747315893&w=2

>>>>> Code: 80 3c 02 00 0f 85 ae 04 00 00 4c 8b a3 a0 00 00 00 48 b8 00 00 00 00
>>>>> 00 fc ff df 49 8d bc 24 b8 01 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f
>>>>> 85 91 04 00 00 49 8b bc 24 b8 01 00 00 e8 2d 70 e6
>>>>> RSP: 0018:ffff8881c2237138 EFLAGS: 00010202
>>>>> RAX: dffffc0000000000 RBX: ffff8881c2bdbc60 RCX: 0000000000000000
>>>>> RDX: 0000000000000037 RSI: ffffffff81c8fa1a RDI: 00000000000001b8
>>>>> RBP: ffff8881c2237160 R08: ffffed10383b25ed R09: ffffed10383b25ec
>>>>> R10: ffffed10383b25ec R11: ffff8881c1d92f63 R12: 0000000000000000
>>>>> R13: ffff8881c2bdbd00 R14: dffffc0000000000 R15: 0000000000000f5e
>>>>> FS:  0000000001a48880(0000) GS:ffff8881dad00000(0000) knlGS:0000000000000000
>>>>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>> CR2: 0000000020b58000 CR3: 00000001c2210000 CR4: 00000000001406e0
>>>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>>> Call Trace:
>>>>>   show_smap+0x167/0x580 fs/proc/task_mmu.c:805
>>>>>   traverse+0x344/0x7b0 fs/seq_file.c:113
>>>>>   seq_read+0xc76/0x1150 fs/seq_file.c:188
>>>>>   do_loop_readv_writev fs/read_write.c:700 [inline]
>>>>>   do_iter_read+0x4bc/0x670 fs/read_write.c:924
>>>>>   vfs_readv+0x175/0x1c0 fs/read_write.c:986
>>>>>   kernel_readv fs/splice.c:362 [inline]
>>>>>   default_file_splice_read+0x539/0xb20 fs/splice.c:417
>>>>>   do_splice_to+0x12e/0x190 fs/splice.c:880
>>>>>   splice_direct_to_actor+0x31c/0x9d0 fs/splice.c:957
>>>>>   do_splice_direct+0x2d4/0x420 fs/splice.c:1066
>>>>>   do_sendfile+0x62a/0xe50 fs/read_write.c:1439
>>>>>   __do_sys_sendfile64 fs/read_write.c:1494 [inline]
>>>>>   __se_sys_sendfile64 fs/read_write.c:1486 [inline]
>>>>>   __x64_sys_sendfile64+0x15d/0x250 fs/read_write.c:1486
>>>>>   do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>>>>>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>>>> RIP: 0033:0x440089
>>>>> Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7
>>>>> 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
>>>>> ff 0f 83 5b 14 fc ff c3 66 2e 0f 1f 84 00 00 00 00
>>>>> RSP: 002b:00007fff3d710a18 EFLAGS: 00000213 ORIG_RAX: 0000000000000028
>>>>> RAX: ffffffffffffffda RBX: 00007fff3d710a20 RCX: 0000000000440089
>>>>> RDX: 0000000020b58000 RSI: 0000000000000003 RDI: 0000000000000003
>>>>> RBP: 00000000006ca018 R08: 0000000000000010 R09: 65732f636f72702f
>>>>> R10: 000000000000ffff R11: 0000000000000213 R12: 0000000000401970
>>>>> R13: 0000000000401a00 R14: 0000000000000000 R15: 0000000000000000
>>>>> Modules linked in:
>>>>> ---[ end trace faf026efd8795e93 ]---
>>>>> RIP: 0010:transparent_hugepage_enabled+0x8c/0x5e0 mm/huge_memory.c:69
>>>>> Code: 80 3c 02 00 0f 85 ae 04 00 00 4c 8b a3 a0 00 00 00 48 b8 00 00 00 00
>>>>> 00 fc ff df 49 8d bc 24 b8 01 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f
>>>>> 85 91 04 00 00 49 8b bc 24 b8 01 00 00 e8 2d 70 e6
>>>>> RSP: 0018:ffff8881c2237138 EFLAGS: 00010202
>>>>> RAX: dffffc0000000000 RBX: ffff8881c2bdbc60 RCX: 0000000000000000
>>>>> RDX: 0000000000000037 RSI: ffffffff81c8fa1a RDI: 00000000000001b8
>>>>> RBP: ffff8881c2237160 R08: ffffed10383b25ed R09: ffffed10383b25ec
>>>>> R10: ffffed10383b25ec R11: ffff8881c1d92f63 R12: 0000000000000000
>>>>> R13: ffff8881c2bdbd00 R14: dffffc0000000000 R15: 0000000000000f5e
>>>>> FS:  0000000001a48880(0000) GS:ffff8881dad00000(0000) knlGS:0000000000000000
>>>>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>> CR2: 0000000020b58000 CR3: 00000001c2210000 CR4: 00000000001406e0
>>>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>>>
>>>>>
>>>>> ---
>>>>> This bug is generated by a bot. It may contain errors.
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>>>>> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx
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>>