Re: WARNING in strp_data_ready

[Tom Herbert]

Did you try the patch I posted?


On Wed, Dec 27, 2017 at 10:25 AM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
> On Wed, Dec 6, 2017 at 4:44 PM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
>>> <john.fastabend@xxxxxxxxx> 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?