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SubjectRe: WARNING in strp_data_ready
On Wed, Dec 27, 2017 at 12:20 PM, Ozgur <ozgur@goosey.org> wrote:
>
>
> 27.12.2017, 23:14, "Dmitry Vyukov" <dvyukov@google.com>:
>> On Wed, Dec 27, 2017 at 9:08 PM, Ozgur <ozgur@goosey.org> wrote:
>>> 27.12.2017, 22:21, "Dmitry Vyukov" <dvyukov@google.com>:
>>>> On Wed, Dec 27, 2017 at 8:09 PM, Tom Herbert <tom@herbertland.com> wrote:
>>>>> Did you try the patch I posted?
>>>>
>>>> Hi Tom,
>>>
>>> Hello Dmitry,
>>>
>>>> No. And I didn't know I need to. Why?
>>>> If you think the patch needs additional testing, you can ask syzbot to
>>>> test it. See https://github.com/google/syzkaller/blob/master/docs/syzbot.md#communication-with-syzbot
>>>> Otherwise proceed with committing it. Or what are we waiting for?
>>>>
>>>> Thanks
>>>
>>> I think we need to fixed patch for crash, in fact check to patch code and test solve the bug.
>>> How do test it because there is no patch in the following bug?
>>
>> Hi Ozgur,
>>
>> I am not sure I completely understand what you mean. But the
>> reproducer for this bug (which one can use for testing) is here:
>> https://groups.google.com/forum/#!topic/syzkaller-bugs/Kxs05ziCpgY
>> Tom also mentions there is some patch for this, but I don't know where
>> it is, it doesn't seem to be referenced from this thread.
>
> Hello Dmitry,
>
> Ah, I'm sorry I don't seen Tom mail and I don't have a patch not tested :)
> I think Tom send patch to only you and are you tested?
>
> kcmsock.c will change and strp_data_ready I think locked.
>
> Tom, please send a patch for me? I can test and inform you.
>
Hi Ozgur,

I reposted the patches as RFC "kcm: Fix lockdep issue". Please test if you can!

Thanks,
Tom

> Regards
>
> Ozgur
>
>>> The fix patch should be for this net/kcm/kcmsock.c file and lock functions must be added calling sk_data_ready ().
>>> Regards
>>>
>>> Ozgur
>>>
>>>>> On Wed, Dec 27, 2017 at 10:25 AM, Dmitry Vyukov <dvyukov@google.com> wrote:
>>>>>> On Wed, Dec 6, 2017 at 4:44 PM, Dmitry Vyukov <dvyukov@google.com> wrote:
>>>>>>>> <john.fastabend@gmail.com> wrote:
>>>>>>>>> On 10/24/2017 08:20 AM, syzbot wrote:
>>>>>>>>>> Hello,
>>>>>>>>>>
>>>>>>>>>> syzkaller hit the following crash on 73d3393ada4f70fa3df5639c8d438f2f034c0ecb
>>>>>>>>>> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
>>>>>>>>>> compiler: gcc (GCC) 7.1.1 20170620
>>>>>>>>>> .config is attached
>>>>>>>>>> Raw console output is attached.
>>>>>>>>>> C reproducer is attached
>>>>>>>>>> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
>>>>>>>>>> for information about syzkaller reproducers
>>>>>>>>>>
>>>>>>>>>> WARNING: CPU: 0 PID: 2996 at ./include/net/sock.h:1505 sock_owned_by_me include/net/sock.h:1505 [inline]
>>>>>>>>>> WARNING: CPU: 0 PID: 2996 at ./include/net/sock.h:1505 sock_owned_by_user include/net/sock.h:1511 [inline]
>>>>>>>>>> WARNING: CPU: 0 PID: 2996 at ./include/net/sock.h:1505 strp_data_ready+0x2b7/0x390 net/strparser/strparser.c:404
>>>>>>>>>> Kernel panic - not syncing: panic_on_warn set ...
>>>>>>>>>>
>>>>>>>>>> CPU: 0 PID: 2996 Comm: syzkaller142210 Not tainted 4.14.0-rc5+ #138
>>>>>>>>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
>>>>>>>>>> Call Trace:
>>>>>>>>>> <IRQ>
>>>>>>>>>> __dump_stack lib/dump_stack.c:16 [inline]
>>>>>>>>>> dump_stack+0x194/0x257 lib/dump_stack.c:52
>>>>>>>>>> panic+0x1e4/0x417 kernel/panic.c:181
>>>>>>>>>> __warn+0x1c4/0x1d9 kernel/panic.c:542
>>>>>>>>>> report_bug+0x211/0x2d0 lib/bug.c:183
>>>>>>>>>> fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:178
>>>>>>>>>> do_trap_no_signal arch/x86/kernel/traps.c:212 [inline]
>>>>>>>>>> do_trap+0x260/0x390 arch/x86/kernel/traps.c:261
>>>>>>>>>> do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:298
>>>>>>>>>> do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:311
>>>>>>>>>> invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:905
>>>>>>>>>> RIP: 0010:sock_owned_by_me include/net/sock.h:1505 [inline]
>>>>>>>>>> RIP: 0010:sock_owned_by_user include/net/sock.h:1511 [inline]
>>>>>>>>>> RIP: 0010:strp_data_ready+0x2b7/0x390 net/strparser/strparser.c:404
>>>>>>>>>> RSP: 0018:ffff8801db206b18 EFLAGS: 00010206
>>>>>>>>>> RAX: ffff8801d1e02080 RBX: ffff8801dad74c48 RCX: 0000000000000000
>>>>>>>>>> RDX: 0000000000000100 RSI: ffff8801d29fa0a0 RDI: ffffffff85cbede0
>>>>>>>>>> RBP: ffff8801db206b38 R08: 0000000000000005 R09: 1ffffffff0ce0bcd
>>>>>>>>>> R10: ffff8801db206a00 R11: dffffc0000000000 R12: ffff8801d29fa000
>>>>>>>>>> R13: ffff8801dad74c50 R14: ffff8801d4350a92 R15: 0000000000000001
>>>>>>>>>> psock_data_ready+0x56/0x70 net/kcm/kcmsock.c:353
>>>>>>>>>
>>>>>>>>> Looks like KCM is calling sk_data_ready() without first taking the
>>>>>>>>> sock lock.
>>>>>>>>>
>>>>>>>>> /* Called with lower sock held */
>>>>>>>>> static void kcm_rcv_strparser(struct strparser *strp, struct sk_buff *skb)
>>>>>>>>> {
>>>>>>>>> [...]
>>>>>>>>> if (kcm_queue_rcv_skb(&kcm->sk, skb)) {
>>>>>>>>>
>>>>>>>>> In this case kcm->sk is not the same lock the comment is referring to.
>>>>>>>>> And kcm_queue_rcv_skb() will eventually call sk_data_ready().
>>>>>>>>>
>>>>>>>>> @Tom, how about wrapping the sk_data_ready call in {lock|release}_sock?
>>>>>>>>> I don't have anything better in mind immediately.
>>>>>>>> The sock locks are taken in reverse order in the send path so so
>>>>>>>> grabbing kcm sock lock with lower lock held to call sk_data_ready may
>>>>>>>> lead to deadlock like I think.
>>>>>>>>
>>>>>>>> It might be possible to change the order in the send path to do this.
>>>>>>>> Something like:
>>>>>>>>
>>>>>>>> trylock on lower socket lock
>>>>>>>> -if trylock fails
>>>>>>>> - release kcm sock lock
>>>>>>>> - lock lower sock
>>>>>>>> - lock kcm sock
>>>>>>>> - call sendpage locked function
>>>>>>>>
>>>>>>>> I admit that dealing with two levels of socket locks in the data path
>>>>>>>> is quite a pain :-)
>>>>>>>
>>>>>>> up
>>>>>>>
>>>>>>> still happening and we've lost 50K+ test VMs on this
>>>>>>
>>>>>> up
>>>>>>
>>>>>> Still happens and number of crashes crossed 60K, can we do something
>>>>>> with this please?

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