==================================================================
BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff85c7f4d0 of 8 bytes by task 23639 on cpu 0:
 data_alloc+0x291/0x2c0 kernel/printk/printk_ringbuffer.c:1088
 prb_reserve+0x897/0xbc0 kernel/printk/printk_ringbuffer.c:1555
 vprintk_store+0x53e/0x800 kernel/printk/printk.c:2228
 vprintk_emit+0xd0/0x5d0 kernel/printk/printk.c:2284
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2318
 vprintk+0x71/0x80 kernel/printk/printk_safe.c:45
 _printk+0x7a/0xa0 kernel/printk/printk.c:2328
 __ext4_msg+0x18a/0x1a0 fs/ext4/super.c:1006
 ext4_fill_super+0x1a1f/0x39b0 fs/ext4/super.c:5718
 get_tree_bdev+0x250/0x2e0 fs/super.c:1619
 ext4_get_tree+0x1c/0x20 fs/ext4/super.c:5735
 vfs_get_tree+0x53/0x1d0 fs/super.c:1784
 do_new_mount+0x227/0x690 fs/namespace.c:3352
 path_mount+0x496/0xb30 fs/namespace.c:3679
 do_mount fs/namespace.c:3692 [inline]
 __do_sys_mount fs/namespace.c:3898 [inline]
 __se_sys_mount+0x27f/0x2d0 fs/namespace.c:3875
 __x64_sys_mount+0x67/0x80 fs/namespace.c:3875
 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+0x63/0x6b

read to 0xffffffff85c7f4d0 of 8 bytes by task 3087 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:478 [inline]
 desc_push_tail kernel/printk/printk_ringbuffer.c:774 [inline]
 desc_reserve kernel/printk/printk_ringbuffer.c:920 [inline]
 prb_reserve+0x229/0xbc0 kernel/printk/printk_ringbuffer.c:1505
 vprintk_store+0x53e/0x800 kernel/printk/printk.c:2228
 vprintk_emit+0xd0/0x5d0 kernel/printk/printk.c:2284
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2318
 vprintk+0x71/0x80 kernel/printk/printk_safe.c:45
 _printk+0x7a/0xa0 kernel/printk/printk.c:2328
 __ext4_msg+0x18a/0x1a0 fs/ext4/super.c:1006
 ext4_put_super+0x91/0x7e0 fs/ext4/super.c:1311
 generic_shutdown_super+0xdb/0x210 fs/super.c:646
 kill_block_super+0x2a/0x60 fs/super.c:1680
 ext4_kill_sb+0x44/0x80 fs/ext4/super.c:7319
 deactivate_locked_super+0x7a/0x1c0 fs/super.c:477
 deactivate_super+0x9b/0xb0 fs/super.c:510
 cleanup_mnt+0x272/0x2e0 fs/namespace.c:1267
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1274
 task_work_run+0x135/0x1a0 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:108 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:201 [inline]
 syscall_exit_to_user_mode+0xbd/0x130 kernel/entry/common.c:212
 do_syscall_64+0xda/0x1d0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00000000002179e8 -> 0x00000000002cae68

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 3087 Comm: syz-executor.2 Not tainted 6.8.0-rc5-syzkaller-00163-gffd2cb6b718e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
==================================================================
EXT4-fs (loop2): unmounting filesystem 00000000-0000-0000-0000-000000000000.
EXT4-fs (loop2): unmounting filesystem 00000000-0000-0000-0000-000000000000.
EXT4-fs (loop2): unmounting filesystem 00000000-0000-0000-0000-000000000000.
EXT4-fs (loop2): unmounting filesystem 00000000-0000-0000-0000-000000000000.
EXT4-fs (loop2): unmounting filesystem 00000000-0000-0000-0000-000000000000.
EXT4-fs (loop2): unmounting filesystem 00000000-0000-0000-0000-000000000000.
EXT4-fs (loop2): unmounting filesystem 00000000-0000-0000-0000-000000000000.
EXT4-fs (loop2): unmounting filesystem 00000000-0000-0000-0000-000000000000.
EXT4-fs (loop2): unmounting filesystem 00000000-0000-0000-0000-000000000000.
EXT4-fs (loop2): unmounting filesystem 00000000-0000-0000-0000-000000000000.
EXT4-fs (loop2): unmounting filesystem 00000000-0000-0000-0000-000000000000.