netdev - Re: [offlist] Re: Crash in netlink/sk_filter_trim

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Message-ID: <CALeDE9OOrZUnaNpzkYPU30iN=4HFQaqEomjf14EO5EtcnHu8OQ@mail.gmail.com>
Date:   Mon, 25 Jun 2018 17:41:27 +0100
From:   Peter Robinson <pbrobinson@...il.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, labbott@...hat.com
Subject: Re: [offlist] Re: Crash in netlink/sk_filter_trim_cap on ARMv7 on 4.18rc1

On Mon, Jun 25, 2018 at 2:39 PM, Peter Robinson <pbrobinson@...il.com> wrote:
> Hi Daniel,
>
>> On 06/24/2018 11:24 AM, Peter Robinson wrote:
>>>>> I'm seeing this netlink/sk_filter_trim_cap crash on ARMv7 across quite
>>>>> a few ARMv7 platforms on Fedora with 4.18rc1. I've tested RPi2/RPi3
>>>>> (doesn't happen on aarch64), AllWinner H3, BeagleBone and a few
>>>>> others, both LPAE/normal kernels.
>>
>> So this is arm32 right?
>
> Correct.
>
>>>>> I'm a bit out of my depth in this part of the kernel but I'm wondering
>>>>> if it's known, I couldn't find anything that looked obvious on a few
>>>>> mailing lists.
>>>>>
>>>>> Peter
>>>>
>>>> Hi Peter
>>>>
>>>> Could you provide symbolic information ?
>>>
>>> I passed in through scripts/decode_stacktrace.sh is that what you were after:
>>>
>>> [    8.673880] Internal error: Oops: a06 [#10] SMP ARM
>>> [    8.673949] ---[ end trace 049df4786ea3140a ]---
>>> [    8.678754] Modules linked in:
>>> [    8.678766] CPU: 1 PID: 206 Comm: systemd-udevd Tainted: G      D
>>>         4.18.0-0.rc1.git0.1.fc29.armv7hl+lpae #1
>>> [    8.678769] Hardware name: Allwinner sun8i Family
>>> [    8.678781] PC is at sk_filter_trim_cap ()
>>> [    8.678790] LR is at   (null)
>>> [    8.709463] pc : lr : psr: 60000013 ()
>>> [    8.715722] sp : c996bd60  ip : 00000000  fp : 00000000
>>> [    8.720939] r10: ee79dc00  r9 : c12c9f80  r8 : 00000000
>>> [    8.726157] r7 : 00000000  r6 : 00000001  r5 : f1648000  r4 : 00000000
>>> [    8.732674] r3 : 00000007  r2 : 00000000  r1 : 00000000  r0 : 00000000
>>> [    8.739193] Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
>>> [    8.746318] Control: 30c5387d  Table: 6e7bc880  DAC: ffe75ece
>>> [    8.752055] Process systemd-udevd (pid: 206, stack limit = 0x(ptrval))
>>> [    8.758574] Stack: (0xc996bd60 to 0xc996c000)
>>
>> Do you have BPF JIT enabled or disabled? Does it happen with disabled?
>
> Enabled, I can test with it disabled, BPF configs bits are:
> CONFIG_BPF_EVENTS=y
> # CONFIG_BPFILTER is not set
> CONFIG_BPF_JIT_ALWAYS_ON=y
> CONFIG_BPF_JIT=y
> CONFIG_BPF_STREAM_PARSER=y
> CONFIG_BPF_SYSCALL=y
> CONFIG_BPF=y
> CONFIG_CGROUP_BPF=y
> CONFIG_HAVE_EBPF_JIT=y
> CONFIG_IPV6_SEG6_BPF=y
> CONFIG_LWTUNNEL_BPF=y
> # CONFIG_NBPFAXI_DMA is not set
> CONFIG_NET_ACT_BPF=m
> CONFIG_NET_CLS_BPF=m
> CONFIG_NETFILTER_XT_MATCH_BPF=m
> # CONFIG_TEST_BPF is not set
>
>> I can see one bug, but your stack trace seems unrelated.
>>
>> Anyway, could you try with this?
>
> Build in process.
>
>> diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
>> index 6e8b716..f6a62ae 100644
>> --- a/arch/arm/net/bpf_jit_32.c
>> +++ b/arch/arm/net/bpf_jit_32.c
>> @@ -1844,7 +1844,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
>>                 /* there are 2 passes here */
>>                 bpf_jit_dump(prog->len, image_size, 2, ctx.target);
>>
>> -       set_memory_ro((unsigned long)header, header->pages);
>> +       bpf_jit_binary_lock_ro(header);
>>         prog->bpf_func = (void *)ctx.target;
>>         prog->jited = 1;
>>         prog->jited_len = image_size;

So with that and the other fix there was no improvement, with those
and the BPF JIT disabled it works, I'm not sure if the two patches
have any effect with the JIT disabled though.

Will look at the other patches shortly, there's been some other issue
introduced between rc1 and rc2 which I have to work out before I can
test those though.

Peter