Re: [syzbot] WARNING in bpf_test_run

[Yonghong Song <yhs@fb.com>]

On 4/1/21 3:05 PM, Yonghong Song wrote:
> 
> 
> On 4/1/21 4:29 AM, syzbot wrote:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit:    36e79851 libbpf: Preserve empty DATASEC BTFs during 
>> static..
>> git tree:       bpf-next
>> console output: 
>> https://syzkaller.appspot.com/x/log.txt?x=1569bb06d00000 
>> kernel config:  
>> https://syzkaller.appspot.com/x/.config?x=7eff0f22b8563a5f 
>> dashboard link: 
>> https://syzkaller.appspot.com/bug?extid=774c590240616eaa3423 
>> syz repro:      
>> https://syzkaller.appspot.com/x/repro.syz?x=17556b7cd00000 
>> C reproducer:   
>> https://syzkaller.appspot.com/x/repro.c?x=1772be26d00000 
>>
>> The issue was bisected to:
>>
>> commit 997acaf6b4b59c6a9c259740312a69ea549cc684
>> Author: Mark Rutland <mark.rutland@arm.com>
>> Date:   Mon Jan 11 15:37:07 2021 +0000
>>
>>      lockdep: report broken irq restoration
>>
>> bisection log:  
>> https://syzkaller.appspot.com/x/bisect.txt?x=10197016d00000 
>> final oops:     
>> https://syzkaller.appspot.com/x/report.txt?x=12197016d00000 
>> console output: 
>> https://syzkaller.appspot.com/x/log.txt?x=14197016d00000 
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the 
>> commit:
>> Reported-by: syzbot+774c590240616eaa3423@syzkaller.appspotmail.com
>> Fixes: 997acaf6b4b5 ("lockdep: report broken irq restoration")
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 0 PID: 8725 at include/linux/bpf-cgroup.h:193 
>> bpf_cgroup_storage_set include/linux/bpf-cgroup.h:193 [inline]
>> WARNING: CPU: 0 PID: 8725 at include/linux/bpf-cgroup.h:193 
>> bpf_test_run+0x65e/0xaa0 net/bpf/test_run.c:109
> 
> I will look at this issue. Thanks!
> 
>> Modules linked in:
>> CPU: 0 PID: 8725 Comm: syz-executor927 Not tainted 
>> 5.12.0-rc4-syzkaller #0
>> Hardware name: Google Google Compute Engine/Google Compute Engine, 
>> BIOS Google 01/01/2011
>> RIP: 0010:bpf_cgroup_storage_set include/linux/bpf-cgroup.h:193 [inline]
>> RIP: 0010:bpf_test_run+0x65e/0xaa0 net/bpf/test_run.c:109
>> Code: e9 29 fe ff ff e8 b2 9d 3a fa 41 83 c6 01 bf 08 00 00 00 44 89 
>> f6 e8 51 a5 3a fa 41 83 fe 08 0f 85 74 fc ff ff e8 92 9d 3a fa <0f> 0b 
>> bd f0 ffff ff e9 5c fd ff ff e8 81 9d 3a fa 83 c5 01 bf 08
>> RSP: 0018:ffffc900017bfaf0 EFLAGS: 00010293
>> RAX: 0000000000000000 RBX: ffffc90000f29000 RCX: 0000000000000000
>> RDX: ffff88801bc68000 RSI: ffffffff8739543e RDI: 0000000000000003
>> RBP: 0000000000000007 R08: 0000000000000008 R09: 0000000000000001
>> R10: ffffffff8739542f R11: 0000000000000000 R12: dffffc0000000000
>> R13: ffff888021dd54c0 R14: 0000000000000008 R15: 0000000000000000
>> FS:  00007f00157d7700(0000) GS:ffff8880b9c00000(0000) 
>> knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 00007f0015795718 CR3: 00000000157ae000 CR4: 00000000001506f0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> Call Trace:
>>   bpf_prog_test_run_skb+0xabc/0x1c70 net/bpf/test_run.c:628
>>   bpf_prog_test_run kernel/bpf/syscall.c:3132 [inline]
>>   __do_sys_bpf+0x218b/0x4f40 kernel/bpf/syscall.c:4411
>>   do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46

Run on my qemu (4 cpus) with C reproducer and I cannot reproduce the 
result. It already ran 30 minutes and still running. Checked the code, 
it is just doing a lot of parallel bpf_prog_test_run's.

The failure is in the below WARN_ON_ONCE code:

175 static inline int bpf_cgroup_storage_set(struct bpf_cgroup_storage
176 
*storage[MAX_BPF_CGROUP_STORAGE_TYPE])
177 {
178         enum bpf_cgroup_storage_type stype;
179         int i, err = 0;
180
181         preempt_disable();
182         for (i = 0; i < BPF_CGROUP_STORAGE_NEST_MAX; i++) {
183                 if 
(unlikely(this_cpu_read(bpf_cgroup_storage_info[i].task) != NULL))
184                         continue;
185
186                 this_cpu_write(bpf_cgroup_storage_info[i].task, 
current);
187                 for_each_cgroup_storage_type(stype)
188 
this_cpu_write(bpf_cgroup_storage_info[i].storage[stype],
189                                        storage[stype]);
190                 goto out;
191         }
192         err = -EBUSY;
193         WARN_ON_ONCE(1);
194
195 out:
196         preempt_enable();
197         return err;
198 }

Basically it shows the stress test triggered a warning due to
limited kernel resource.

>>   entry_SYSCALL_64_after_hwframe+0x44/0xae
>> RIP: 0033:0x446199
>> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 00 00 90 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 ffff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
>> RSP: 002b:00007f00157d72f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
>> RAX: ffffffffffffffda RBX: 00000000004cb440 RCX: 0000000000446199
>> RDX: 0000000000000028 RSI: 0000000020000080 RDI: 000000000000000a
>> RBP: 000000000049b074 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000246 R12: f9abde7200f522cd
>> R13: 3952ddf3af240c07 R14: 1631e0d82d3fa99d R15: 00000000004cb448
>>
>>
>> ---
>> This report is generated by a bot. It may contain errors.
>> See 
>> https://goo.gl/tpsmEJ   
>> for more information about syzbot.
>> syzbot engineers can be reached at syzkaller@googlegroups.com.
>>
>> syzbot will keep track of this issue. See:
>> https://goo.gl/tpsmEJ#status   
>> for how to communicate with syzbot.
>> For information about bisection process see: 
>> https://goo.gl/tpsmEJ#bisection 
>> syzbot can test patches for this issue, for details see:
>> https://goo.gl/tpsmEJ#testing-patches 
>>