syzbot

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BUG: KCSAN: data-race in ppp_asynctty_receive / tty_set_termios

write to 0xffff8881185b6108 of 44 bytes by task 11143 on cpu 1:
 tty_set_termios+0xc0/0x8c0 drivers/tty/tty_ioctl.c:335
 set_termios+0x496/0x4e0 drivers/tty/tty_ioctl.c:512
 tty_mode_ioctl+0x379/0x5c0 drivers/tty/tty_ioctl.c:-1
 ppp_asynctty_ioctl+0x13f/0x2d0 drivers/net/ppp/ppp_async.c:324
 tty_ioctl+0x842/0xb80 drivers/tty/tty_io.c:2801
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:893
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:893
 x64_sys_call+0x19a8/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881185b6108 of 4 bytes by task 4091 on cpu 0:
 ppp_async_input drivers/net/ppp/ppp_async.c:905 [inline]
 ppp_asynctty_receive+0x75c/0xd40 drivers/net/ppp/ppp_async.c:342
 tty_ldisc_receive_buf+0xbf/0xf0 drivers/tty/tty_buffer.c:391
 tty_port_default_receive_buf+0x59/0x90 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:445 [inline]
 flush_to_ldisc+0x141/0x360 drivers/tty/tty_buffer.c:495
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3321
 worker_thread+0x582/0x770 kernel/workqueue.c:3402
 kthread+0x489/0x510 kernel/kthread.c:464
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x00000500 -> 0x00038000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 4091 Comm: kworker/u8:21 Not tainted 6.16.0-rc5-syzkaller-00266-g3f31a806a62e #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: events_unbound flush_to_ldisc
==================================================================
erspan0 (unregistering): left allmulticast mode
erspan0 (unregistering): left promiscuous mode
bond0 (unregistering): (slave bond_slave_0): Releasing backup interface
bond_slave_0: left allmulticast mode
bond0 (unregistering): (slave bond_slave_1): Releasing backup interface
bond_slave_1: left allmulticast mode
bond0 (unregistering): (slave macvlan1): Releasing backup interface
veth1_vlan: left allmulticast mode
bond0 (unregistering): Released all slaves
tipc: Disabling bearer <udp:£>
tipc: Left network mode
IPVS: stopping backup sync thread 7672 ...
hsr_slave_0: left promiscuous mode
hsr_slave_1: left promiscuous mode
batman_adv: batadv0: Removing interface: team0
batman_adv: batadv0: Removing interface: batadv_slave_0
batman_adv: batadv0: Removing interface: batadv_slave_1
team0 (unregistering): Port device team_slave_1 removed
team0 (unregistering): Port device team_slave_0 removed
netdevsim netdevsim6 eth3 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim6 eth2 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim6 eth1 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim6 eth0 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim8 netdevsim3 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim8 netdevsim2 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim8 netdevsim1 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
netdevsim netdevsim8 netdevsim0 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
bridge_slave_1: left allmulticast mode
bridge_slave_1: left promiscuous mode
bridge0: port 2(bridge_slave_1) entered disabled state
bridge_slave_0: left allmulticast mode
bridge_slave_0: left promiscuous mode
bridge0: port 1(bridge_slave_0) entered disabled state
bridge_slave_1: left allmulticast mode
bridge_slave_1: left promiscuous mode
bridge0: port 2(bridge_slave_1) entered disabled state
bridge_slave_0: left allmulticast mode
bridge_slave_0: left promiscuous mode
bridge0: port 1(bridge_slave_0) entered disabled state
bond0 (unregistering): (slave geneve1): Releasing backup interface
bond0 (unregistering): Released all slaves
bond1 (unregistering): Released all slaves
bond0 (unregistering): (slave bond_slave_0): Releasing backup interface
bond0 (unregistering): (slave bond_slave_1): Releasing backup interface
bond0 (unregistering): Released all slaves
bond2 (unregistering): (slave gretap1): Releasing active interface
bond0 (unregistering): (slave geneve1): Releasing backup interface
geneve1 (unregistering): left allmulticast mode
bond0 (unregistering): (slave bond_slave_0): Releasing backup interface
bond_slave_0: left allmulticast mode
bond0 (unregistering): (slave bond_slave_1): Releasing backup interface
bond_slave_1: left allmulticast mode
bond0 (unregistering): Released all slaves
bond1 (unregistering): Released all slaves
bond2 (unregistering): Released all slaves
bond3 (unregistering): (slave vcan1): Releasing backup interface
bond3 (unregistering): Released all slaves
bond0 (unregistering): (slave bond_slave_0): Releasing backup interface
bond0 (unregistering): (slave bond_slave_1): Releasing backup interface
bond0 (unregistering): Released all slaves
tipc: Left network mode
tipc: Disabling bearer <udp:syz2>
tipc: Left network mode
hsr_slave_0: left promiscuous mode
hsr_slave_1: left promiscuous mode
hsr_slave_0: left promiscuous mode
hsr_slave_1: left promiscuous mode
batman_adv: batadv0: Interface deactivated: batadv_slave_0
batman_adv: batadv0: Removing interface: batadv_slave_0
batman_adv: batadv0: Interface deactivated: batadv_slave_1
batman_adv: batadv0: Removing interface: batadv_slave_1
hsr_slave_0: left promiscuous mode
hsr_slave_1: left promiscuous mode
batman_adv: batadv0: Removing interface: batadv_slave_0
batman_adv: batadv0: Removing interface: batadv_slave_1
batman_adv: batadv0: Removing interface: ipvlan2
hsr_slave_0: left promiscuous mode
hsr_slave_1: left promiscuous mode
batman_adv: batadv0: Removing interface: batadv_slave_0
batman_adv: batadv0: Removing interface: batadv_slave_1
veth1_macvtap: left promiscuous mode
veth0_macvtap: left promiscuous mode
veth1_vlan: left promiscuous mode
veth0_vlan: left promiscuous mode
veth1_macvtap: left promiscuous mode
veth0_macvtap: left promiscuous mode
veth1_vlan: left promiscuous mode
veth0_vlan: left promiscuous mode
team0 (unregistering): Port device team_slave_1 removed
team0 (unregistering): Port device team_slave_0 removed
team0 (unregistering): Port device team_slave_1 removed
team0 (unregistering): Port device team_slave_0 removed
team0 (unregistering): Port device team_slave_1 removed
team0 (unregistering): Port device team_slave_0 removed
IPVS: stop unused estimator thread 0...