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

write to 0xffffffff86883608 of 8 bytes by task 11344 on cpu 1:
 data_alloc+0x27d/0x2b0 kernel/printk/printk_ringbuffer.c:1096
 prb_reserve+0x808/0xaf0 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2475
 __ext4_std_error+0x346/0x370 fs/ext4/super.c:956
 ext4_free_inode+0x79e/0x870 fs/ext4/ialloc.c:361
 ext4_evict_inode+0xb0c/0xd90 fs/ext4/inode.c:306
 evict+0x2e0/0x550 fs/inode.c:810
 iput_final fs/inode.c:1897 [inline]
 iput+0x447/0x5b0 fs/inode.c:1923
 ext4_process_orphan+0x1a9/0x1c0 fs/ext4/orphan.c:360
 ext4_orphan_cleanup+0x6a8/0xa00 fs/ext4/orphan.c:474
 __ext4_fill_super fs/ext4/super.c:5609 [inline]
 ext4_fill_super+0x3260/0x35d0 fs/ext4/super.c:5728
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1692
 get_tree_bdev+0x1f/0x30 fs/super.c:1715
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5760
 vfs_get_tree+0x54/0x1d0 fs/super.c:1815
 do_new_mount+0x207/0x5e0 fs/namespace.c:3808
 path_mount+0x4a4/0xb20 fs/namespace.c:4123
 do_mount fs/namespace.c:4136 [inline]
 __do_sys_mount fs/namespace.c:4347 [inline]
 __se_sys_mount+0x28f/0x2e0 fs/namespace.c:4324
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4324
 x64_sys_call+0x2b4d/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86883608 of 8 bytes by task 4762 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:482 [inline]
 desc_push_tail kernel/printk/printk_ringbuffer.c:778 [inline]
 desc_reserve kernel/printk/printk_ringbuffer.c:924 [inline]
 prb_reserve+0x221/0xaf0 kernel/printk/printk_ringbuffer.c:1619
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2475
 __ext4_error_inode+0x30f/0x3f0 fs/ext4/super.c:839
 __check_block_validity fs/ext4/inode.c:390 [inline]
 ext4_map_blocks+0xa14/0xd00 fs/ext4/inode.c:-1
 ext4_getblk+0x114/0x510 fs/ext4/inode.c:978
 ext4_bread+0x28/0x110 fs/ext4/inode.c:1041
 ext4_quota_read+0xe8/0x260 fs/ext4/super.c:7255
 read_blk fs/quota/quota_tree.c:61 [inline]
 remove_tree+0x129/0x1120 fs/quota/quota_tree.c:555
 qtree_delete_dquot fs/quota/quota_tree.c:617 [inline]
 qtree_release_dquot+0x16e/0x180 fs/quota/quota_tree.c:787
 v2_release_dquot+0x98/0xd0 fs/quota/quota_v2.c:391
 dquot_release+0x10e/0x210 fs/quota/dquot.c:537
 ext4_release_dquot+0x1e4/0x460 fs/ext4/super.c:-1
 quota_release_workfn+0x253/0x530 fs/quota/dquot.c:840
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x486/0x510 kernel/kthread.c:463
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x0000000000171a30 -> 0x0000000000228d48

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 4762 Comm: kworker/u8:16 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: events_unbound quota_release_workfn
==================================================================
EXT4-fs error (device loop5): ext4_map_blocks:778: inode #3: block 1: comm kworker/u8:16: lblock 1 mapped to illegal pblock 1 (length 1)
EXT4-fs error (device loop5): ext4_release_dquot:6973: comm kworker/u8:16: Failed to release dquot type 0