syzbot

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BUG: KCSAN: data-race in n_tty_check_unthrottle / n_tty_receive_buf_common

write to 0xffff8881160d25dc of 4 bytes by task 26211 on cpu 0:
 tty_set_flow_change drivers/tty/tty.h:59 [inline]
 n_tty_check_unthrottle+0xd7/0x1c0 drivers/tty/n_tty.c:280
 n_tty_read+0xf0b/0x11d0 drivers/tty/n_tty.c:2302
 iterate_tty_read drivers/tty/tty_io.c:862 [inline]
 tty_read+0x15b/0x480 drivers/tty/tty_io.c:937
 call_read_iter include/linux/fs.h:2104 [inline]
 new_sync_read fs/read_write.c:395 [inline]
 vfs_read+0x5bc/0x6b0 fs/read_write.c:476
 ksys_read+0xeb/0x1b0 fs/read_write.c:619
 __do_sys_read fs/read_write.c:629 [inline]
 __se_sys_read fs/read_write.c:627 [inline]
 __x64_sys_read+0x42/0x50 fs/read_write.c:627
 x64_sys_call+0x27ad/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:1
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff8881160d25dc of 4 bytes by task 26214 on cpu 1:
 n_tty_receive_buf_common+0xae5/0xbd0
 n_tty_receive_buf+0x30/0x40 drivers/tty/n_tty.c:1769
 tiocsti+0x166/0x1d0 drivers/tty/tty_io.c:2299
 tty_ioctl+0x415/0xbe0 drivers/tty/tty_io.c:2717
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:904 [inline]
 __se_sys_ioctl+0xd3/0x150 fs/ioctl.c:890
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:890
 x64_sys_call+0x155d/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 26214 Comm: syz-executor.3 Not tainted 6.9.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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