syzbot

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BUG: KCSAN: data-race in __process_echoes / n_tty_write

write to 0xffffc90001776280 of 8 bytes by task 6826 on cpu 0:
 __process_echoes+0x688/0x6b0 drivers/tty/n_tty.c:746
 flush_echoes drivers/tty/n_tty.c:807 [inline]
 __receive_buf drivers/tty/n_tty.c:1642 [inline]
 n_tty_receive_buf_common+0x8f9/0xbe0 drivers/tty/n_tty.c:1739
 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1785
 tty_ldisc_receive_buf+0x63/0x100 drivers/tty/tty_buffer.c:387
 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+0x1ce/0x410 drivers/tty/tty_buffer.c:495
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3317
 worker_thread+0x51d/0x6f0 kernel/workqueue.c:3398
 kthread+0x4ae/0x520 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffffc90001776280 of 8 bytes by task 19615 on cpu 1:
 process_echoes drivers/tty/n_tty.c:784 [inline]
 n_tty_write+0x16c/0xb80 drivers/tty/n_tty.c:2375
 iterate_tty_write drivers/tty/tty_io.c:1015 [inline]
 file_tty_write+0x37a/0x680 drivers/tty/tty_io.c:1090
 tty_write+0x28/0x30 drivers/tty/tty_io.c:1111
 new_sync_write fs/read_write.c:586 [inline]
 vfs_write+0x77b/0x920 fs/read_write.c:679
 ksys_write+0xe8/0x1b0 fs/read_write.c:731
 __do_sys_write fs/read_write.c:742 [inline]
 __se_sys_write fs/read_write.c:739 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:739
 x64_sys_call+0x287e/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0x0000000000000007

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 19615 Comm: syz.8.14414 Not tainted 6.14.0-rc1-syzkaller-00026-gd009de7d5428 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
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netlink: 28 bytes leftover after parsing attributes in process `syz.8.14414'.
netlink: 28 bytes leftover after parsing attributes in process `syz.8.14414'.
netlink: 28 bytes leftover after parsing attributes in process `syz.8.14414'.
netlink: 28 bytes leftover after parsing attributes in process `syz.8.14414'.
__nla_validate_parse: 2 callbacks suppressed
netlink: 28 bytes leftover after parsing attributes in process `syz.8.14414'.
netlink: 28 bytes leftover after parsing attributes in process `syz.8.14414'.
netlink: 28 bytes leftover after parsing attributes in process `syz.8.14414'.