Re: mm: GPF in __insert_vmap_area

[Dmitry Vyukov <dvyukov@google.com>]

On Mon, Sep 5, 2016 at 1:30 AM, zijun_hu <zijun_hu@zoho.com> wrote:
> On 09/03/2016 08:15 PM, Dmitry Vyukov wrote:
>> Hello,
>>
>> While running syzkaller fuzzer I've got the following GPF:
>>
>> general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN
>> Dumping ftrace buffer:
>>    (ftrace buffer empty)
>> Modules linked in:
>> CPU: 2 PID: 4268 Comm: syz-executor Not tainted 4.8.0-rc3-next-20160825+ #8
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>> task: ffff88006a6527c0 task.stack: ffff880052630000
>> RIP: 0010:[<ffffffff82e1ccd6>]  [<ffffffff82e1ccd6>]
>> __list_add_valid+0x26/0xd0 lib/list_debug.c:23
>> RSP: 0018:ffff880052637a18  EFLAGS: 00010202
>> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc90001c87000
>> RDX: 0000000000000001 RSI: ffff88001344cdb0 RDI: 0000000000000008
>> RBP: ffff880052637a30 R08: 0000000000000001 R09: 0000000000000000
>> R10: 0000000000000000 R11: ffffffff8a5deee0 R12: ffff88006cc47230
>> R13: ffff88001344cdb0 R14: ffff88006cc47230 R15: 0000000000000000
>> FS:  00007fbacc97e700(0000) GS:ffff88006d200000(0000) knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 0000000020de7000 CR3: 000000003c4d2000 CR4: 00000000000006e0
>> DR0: 000000000000001e DR1: 000000000000001e DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
>> Stack:
>>  ffff88006cc47200 ffff88001344cd98 ffff88006cc47200 ffff880052637a78
>>  ffffffff817bc6d1 ffff88006cc47208 ffffed000d988e41 ffff88006cc47208
>>  ffff88006cc3e680 ffffc900035b7000 ffffc900035a7000 ffff88006cc47200
>> Call Trace:
>>  [<     inline     >] __list_add_rcu include/linux/rculist.h:51
>>  [<     inline     >] list_add_rcu include/linux/rculist.h:78
>>  [<ffffffff817bc6d1>] __insert_vmap_area+0x1c1/0x3c0 mm/vmalloc.c:340
>>  [<ffffffff817bf544>] alloc_vmap_area+0x614/0x890 mm/vmalloc.c:458
>>  [<ffffffff817bf8a8>] __get_vm_area_node+0xe8/0x340 mm/vmalloc.c:1377
>>  [<ffffffff817c332a>] __vmalloc_node_range+0xaa/0x6d0 mm/vmalloc.c:1687
>>  [<     inline     >] __vmalloc_node mm/vmalloc.c:1736
>>  [<ffffffff817c39ab>] __vmalloc+0x5b/0x70 mm/vmalloc.c:1742
>>  [<ffffffff8166ae9c>] bpf_prog_alloc+0x3c/0x190 kernel/bpf/core.c:82
>>  [<ffffffff85c40ba9>] bpf_prog_create_from_user+0xa9/0x2c0
>> net/core/filter.c:1132
>>  [<     inline     >] seccomp_prepare_filter kernel/seccomp.c:373
>>  [<     inline     >] seccomp_prepare_user_filter kernel/seccomp.c:408
>>  [<     inline     >] seccomp_set_mode_filter kernel/seccomp.c:737
>>  [<ffffffff815d7687>] do_seccomp+0x317/0x1800 kernel/seccomp.c:787
>>  [<ffffffff815d8f84>] prctl_set_seccomp+0x34/0x60 kernel/seccomp.c:830
>>  [<     inline     >] SYSC_prctl kernel/sys.c:2157
>>  [<ffffffff813ccf8f>] SyS_prctl+0x82f/0xc80 kernel/sys.c:2075
>>  [<ffffffff86e10700>] entry_SYSCALL_64_fastpath+0x23/0xc1
>> Code: 00 00 00 00 00 55 48 b8 00 00 00 00 00 fc ff df 48 89 e5 41 54
>> 49 89 fc 48 8d 7a 08 53 48 89 d3 48 89 fa 48 83 ec 08 48 c1 ea 03 <80>
>> 3c 02 00 75 7c 48 8b 53 08 48 39 f2 75 37 48 89 f2 48 b8 00
>> RIP  [<ffffffff82e1ccd6>] __list_add_valid+0x26/0xd0 lib/list_debug.c:23
>>  RSP <ffff880052637a18>
>> ---[ end trace 983e625f02f00d9f ]---
>> Kernel panic - not syncing: Fatal exception
>>
>> On commit 0f98f121e1670eaa2a2fbb675e07d6ba7f0e146f of linux-next.
>> Unfortunately it is not reproducible.
>> The crashing line is:
>>         CHECK_DATA_CORRUPTION(next->prev != prev,
>>
>> It crashed on KASAN check at (%rax, %rdx), this address corresponds to
>> next address = 0x8. So next was ~NULL.
>>
> Hi Dmitry
> i am not sure for the real reason of the GPF panic
> i have been browsing mm/vmalloc.c recently and have found several bugs perhaps
> i hope it maybe help you
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 91f44e7..1429ee6 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -321,10 +321,10 @@ static void __insert_vmap_area(struct vmap_area *va)
>
>                 parent = *p;
>                 tmp_va = rb_entry(parent, struct vmap_area, rb_node);
> -               if (va->va_start < tmp_va->va_end)
> -                       p = &(*p)->rb_left;
> -               else if (va->va_end > tmp_va->va_start)
> -                       p = &(*p)->rb_right;
> +               if (va->va_end <= tmp_va->va_start)
> +                       p = &parent->rb_left;
> +               else if (va->va_start >= tmp_va->va_end)
> +                       p = &parent->rb_right;
>                 else
>                         BUG();
>         }
> @@ -432,6 +432,9 @@ nocache:
>
>                 if (!first)
>                         goto found;
> +
> +               if (addr > first->va_end)
> +                       first = list_next_entry(first, list);
>         }
>
>         /* from the starting point, walk areas until a suitable hole is found */
> @@ -594,7 +597,9 @@ static unsigned long lazy_max_pages(void)
>  {
>         unsigned int log;
>
> -       log = fls(num_online_cpus());
> +       log = num_online_cpus();
> +       if (log > 1)
> +               log = (unsigned int)get_count_order(log);
>
>         return log * (32UL * 1024 * 1024 / PAGE_SIZE);
>  }

Hi,

Unfortunately the bug is not reproducible, so I can't test your patches.
However, if you see bugs in mm code, please mail these patches for review.

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