syzbot

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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff8613fa58 of 8 bytes by task 889 on cpu 1:
 prb_reserve+0x740/0xb60
 vprintk_store+0x53f/0x810 kernel/printk/printk.c:2269
 vprintk_emit+0x10c/0x5e0 kernel/printk/printk.c:2329
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2363
 vprintk+0x75/0x80 kernel/printk/printk_safe.c:45
 _printk+0x7a/0xa0 kernel/printk/printk.c:2373
 __ext4_msg+0x18e/0x1a0 fs/ext4/super.c:1006
 ext4_put_super+0x91/0x7e0 fs/ext4/super.c:1311
 generic_shutdown_super+0xde/0x210 fs/super.c:641
 kill_block_super+0x2a/0x70 fs/super.c:1675
 ext4_kill_sb+0x44/0x80 fs/ext4/super.c:7327
 deactivate_locked_super+0x7d/0x1c0 fs/super.c:472
 deactivate_super+0x9f/0xb0 fs/super.c:505
 cleanup_mnt+0x272/0x2e0 fs/namespace.c:1267
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1274
 task_work_run+0x13a/0x1a0 kernel/task_work.c:180
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0xbe/0x130 kernel/entry/common.c:218
 do_syscall_64+0xda/0x1d0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff8613fa58 of 8 bytes by task 2587 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:486 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1874 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1922 [inline]
 _prb_read_valid+0x1ec/0xba0 kernel/printk/printk_ringbuffer.c:2113
 prb_read_valid+0x3d/0x60 kernel/printk/printk_ringbuffer.c:2182
 printk_get_next_message+0xd8/0x6f0 kernel/printk/printk.c:2825
 console_emit_next_record kernel/printk/printk.c:2880 [inline]
 console_flush_all+0x1c7/0x710 kernel/printk/printk.c:2979
 console_unlock+0x7b/0x280 kernel/printk/printk.c:3048
 do_con_write+0x2582/0x25f0
 con_put_char+0x39/0x60 drivers/tty/vt/vt.c:3442
 tty_put_char+0x67/0xc0 drivers/tty/tty_io.c:3167
 __process_echoes+0x12c/0x6b0 drivers/tty/n_tty.c:724
 commit_echoes drivers/tty/n_tty.c:772 [inline]
 n_tty_receive_char+0x608/0x680 drivers/tty/n_tty.c:1437
 n_tty_receive_buf_standard+0x4bd/0x2e30 drivers/tty/n_tty.c:1606
 __receive_buf drivers/tty/n_tty.c:1630 [inline]
 n_tty_receive_buf_common+0x7e5/0xbd0 drivers/tty/n_tty.c:1729
 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1775
 tty_ldisc_receive_buf+0x63/0x100 drivers/tty/tty_buffer.c:387
 paste_selection+0x1de/0x2e0 drivers/tty/vt/selection.c:418
 tioclinux+0x2d6/0x430 drivers/tty/vt/vt.c:3354
 vt_ioctl+0x84f/0x1810 drivers/tty/vt/vt_ioctl.c:761
 tty_ioctl+0x821/0xbe0 drivers/tty/tty_io.c:2803
 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: 0x0000000000001f65 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 2587 Comm: syz-executor.4 Tainted: G        W          6.9.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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