Re: [syzbot] [apparmor?] [ext4?] INFO: rcu detected stall in sys_getdents64

[Nikolay Aleksandrov <razor@blackwall.org>]

On 10/10/2024 12:48, Tetsuo Handa wrote:
> This is a printk() flooding problem in bridge driver. Should consider using ratelimit.
> 
> #syz set subsystems: net
> 

It should already be ratelimited, the code that prints is:
                       if (net_ratelimit())
                                br_warn(br, "received packet on %s with own address as source address (addr:%pM, vlan:%u)\n",
                                        source->dev->name, addr, vid);

Cheers,
 Nik

> On 2024/10/10 12:27, syzbot wrote:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit:    fc20a3e57247 Merge tag 'for-linus-6.12a-rc2-tag' of git://..
>> git tree:       upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=1083b380580000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=ba92623fdea824c9
>> dashboard link: https://syzkaller.appspot.com/bug?extid=17bc8c5157022e18da8b
>> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=135f7d27980000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1483b380580000
>>
>> Downloadable assets:
>> disk image: https://storage.googleapis.com/syzbot-assets/2ad9af7b84b4/disk-fc20a3e5.raw.xz
>> vmlinux: https://storage.googleapis.com/syzbot-assets/1afa462ca485/vmlinux-fc20a3e5.xz
>> kernel image: https://storage.googleapis.com/syzbot-assets/75c0900b4786/bzImage-fc20a3e5.xz
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+17bc8c5157022e18da8b@syzkaller.appspotmail.com
>>
>> bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
>> rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
>> rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5244/1:b..l
>> rcu: 	(detected by 1, t=10503 jiffies, g=5253, q=1466 ncpus=2)
>> task:syz-executor116 state:R  running task     stack:18800 pid:5244  tgid:5244  ppid:5243   flags:0x00000002
> (...snipped...)
>> net_ratelimit: 33488 callbacks suppressed
>> bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
>> bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
>> bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
>> bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
>> bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
>> bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
>> bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
>> bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
>> bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
>> bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
> 
>