Re: [PATCH RESEND net] bonding: fix missed rcu protection

[Jonathan Toppins <jtoppins@redhat.com>]

On 5/13/22 06:33, Hangbin Liu wrote:
> When removing the rcu_read_lock in bond_ethtool_get_ts_info(), I didn't
> notice it could be called via setsockopt, which doesn't hold rcu lock,
> as syzbot pointed:
> 
>    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
>     __sys_setsockopt+0x55e/0x6a0 net/socket.c:2223
>     __do_sys_setsockopt net/socket.c:2238 [inline]
>     __se_sys_setsockopt net/socket.c:2235 [inline]
>     __x64_sys_setsockopt+0xba/0x150 net/socket.c:2235
>     do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>     do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>     entry_SYSCALL_64_after_hwframe+0x44/0xae
>    RIP: 0033:0x7f8902c8eb39
> 
> Fix it by adding rcu_read_lock during the whole slave dev get_ts_info period.
> 
> Reported-by: syzbot+92beb3d46aab498710fa@syzkaller.appspotmail.com
> Fixes: aa6034678e87 ("bonding: use rcu_dereference_rtnl when get bonding active slave")
> Suggested-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Acked-by: Jonathan Toppins <jtoppins@redhat.com>