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

write to 0xffffffff86c6e760 of 8 bytes by task 21976 on cpu 0:
 data_alloc+0x308/0x380 kernel/printk/printk_ringbuffer.c:1130
 prb_reserve+0x8e3/0xaf0 kernel/printk/printk_ringbuffer.c:1727
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 __ext4_error+0x225/0x2e0 fs/ext4/super.c:829
 ext4_orphan_get+0x1cb/0x430 fs/ext4/ialloc.c:1425
 ext4_orphan_cleanup+0x5fe/0xa10 fs/ext4/orphan.c:465
 __ext4_fill_super fs/ext4/super.c:5705 [inline]
 ext4_fill_super+0x33ab/0x3760 fs/ext4/super.c:5828
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1640
 get_tree_bdev+0x1f/0x30 fs/super.c:1663
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5860
 vfs_get_tree+0x57/0x1d0 fs/super.c:1700
 fc_mount fs/namespace.c:1198 [inline]
 do_new_mount_fc fs/namespace.c:3765 [inline]
 do_new_mount+0x288/0x8d0 fs/namespace.c:3841
 path_mount+0x4ad/0xb90 fs/namespace.c:4161
 do_mount fs/namespace.c:4174 [inline]
 __do_sys_mount fs/namespace.c:4390 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4367
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4367
 x64_sys_call+0x2d61/0x3020 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86c6e760 of 8 bytes by task 21974 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:496 [inline]
 desc_push_tail kernel/printk/printk_ringbuffer.c:792 [inline]
 desc_reserve kernel/printk/printk_ringbuffer.c:938 [inline]
 prb_reserve+0x21a/0xaf0 kernel/printk/printk_ringbuffer.c:1677
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 ext4_setup_super+0x572/0x580 fs/ext4/super.c:3155
 __ext4_fill_super fs/ext4/super.c:5622 [inline]
 ext4_fill_super+0x29ab/0x3760 fs/ext4/super.c:5828
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1640
 get_tree_bdev+0x1f/0x30 fs/super.c:1663
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5860
 vfs_get_tree+0x57/0x1d0 fs/super.c:1700
 fc_mount fs/namespace.c:1198 [inline]
 do_new_mount_fc fs/namespace.c:3765 [inline]
 do_new_mount+0x288/0x8d0 fs/namespace.c:3841
 path_mount+0x4ad/0xb90 fs/namespace.c:4161
 do_mount fs/namespace.c:4174 [inline]
 __do_sys_mount fs/namespace.c:4390 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4367
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4367
 x64_sys_call+0x2d61/0x3020 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xfffffffffffdf590 -> 0x0000000000099a38

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 21974 Comm: syz.1.4476 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================
[EXT4 FS bs=1024, gc=1, bpg=131072, ipg=32, mo=a802c028, mo2=0002]
System zones: 0-1, 3-12
EXT4-fs (loop1): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.