Re: [syzbot] WARNING: suspicious RCU usage in bond_ethtool_get_ts_info

[Hangbin Liu <liuhangbin@gmail.com>]

Remove bpf guys from cc list.

On Thu, May 12, 2022 at 12:35:28PM -0700, syzbot wrote:
> 
> The issue was bisected to:
> 
> commit aa6034678e873db8bd5c5a4b73f8b88c469374d6
> Author: Hangbin Liu <liuhangbin@gmail.com>
> Date:   Fri Jan 21 08:25:18 2022 +0000
> 
>     bonding: use rcu_dereference_rtnl when get bonding active slave
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=16fce349f00000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=15fce349f00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=11fce349f00000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+92beb3d46aab498710fa@syzkaller.appspotmail.com
> Fixes: aa6034678e87 ("bonding: use rcu_dereference_rtnl when get bonding active slave")
> 
> =============================
> WARNING: suspicious RCU usage
> 5.18.0-rc5-syzkaller-01392-g01f4685797a5 #0 Not tainted
> -----------------------------
> include/net/bonding.h:353 suspicious rcu_dereference_check() usage!
> 
> other info that might help us debug this:
> 
> 
> rcu_scheduler_active = 2, debug_locks = 1
> 1 lock held by syz-executor317/3599:
>  #0: ffff88801de78130 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1680 [inline]
>  #0: ffff88801de78130 (sk_lock-AF_INET){+.+.}-{0:0}, at: sock_setsockopt+0x1e3/0x2ec0 net/core/sock.c:1066
> 
> stack backtrace:
> CPU: 0 PID: 3599 Comm: syz-executor317 Not tainted 5.18.0-rc5-syzkaller-01392-g01f4685797a5 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
>  bond_option_active_slave_get_rcu include/net/bonding.h:353 [inline]
>  bond_ethtool_get_ts_info+0x32c/0x3a0 drivers/net/bonding/bond_main.c:5595
>  __ethtool_get_ts_info+0x173/0x240 net/ethtool/common.c:554
>  ethtool_get_phc_vclocks+0x99/0x110 net/ethtool/common.c:568
>  sock_timestamping_bind_phc net/core/sock.c:869 [inline]
>  sock_set_timestamping+0x3a3/0x7e0 net/core/sock.c:916
>  sock_setsockopt+0x543/0x2ec0 net/core/sock.c:1221

Oh, I forgot to check setsockopt path...

Hi Vladimir, Jay,

Do you think if I should revert my previous commit, or just add
rcu_read_lock()/rcu_read_unlock() back to bond_ethtool_get_ts_info()?

Thanks
Hangbin