syzbot

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BUG: KCSAN: data-race in ppp_asynctty_receive / tty_set_termios

write to 0xffff888103fa7d08 of 44 bytes by task 11623 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+0x845/0xb80 drivers/tty/tty_io.c:2801
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0xce/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 0xffff888103fa7d08 of 4 bytes by task 6914 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: 6914 Comm: kworker/u8:5 Tainted: G        W           6.16.0-rc5-syzkaller-00121-gbc9ff192a6c9 #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: events_unbound flush_to_ldisc
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