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

write to 0xffffffff8687b1e0 of 8 bytes by task 25336 on cpu 0:
 data_alloc+0x271/0x2b0 kernel/printk/printk_ringbuffer.c:1095
 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_error+0x248/0x320 fs/ext4/super.c:817
 ext4_read_block_bitmap_nowait+0x1d5/0x680 fs/ext4/balloc.c:482
 ext4_mb_init_cache+0x240/0xb60 fs/ext4/mballoc.c:1337
 ext4_mb_init_group+0x223/0x3b0 fs/ext4/mballoc.c:1543
 ext4_mb_prefetch_fini+0xf3/0x160 fs/ext4/mballoc.c:2790
 ext4_mb_regular_allocator+0x22b3/0x2300 fs/ext4/mballoc.c:3001
 ext4_mb_new_blocks+0x800/0x2050 fs/ext4/mballoc.c:6215
 ext4_new_meta_blocks+0xc3/0x1b0 fs/ext4/balloc.c:750
 ext4_ext_grow_indepth fs/ext4/extents.c:1329 [inline]
 ext4_ext_create_new_leaf fs/ext4/extents.c:1433 [inline]
 ext4_ext_insert_extent+0x9ec/0x29b0 fs/ext4/extents.c:2115
 ext4_ext_map_blocks+0x1091/0x3620 fs/ext4/extents.c:4400
 ext4_map_create_blocks fs/ext4/inode.c:520 [inline]
 ext4_map_blocks+0x5ab/0xd00 fs/ext4/inode.c:706
 ext4_getblk+0x114/0x510 fs/ext4/inode.c:853
 ext4_bread+0x28/0x110 fs/ext4/inode.c:916
 ext4_quota_write+0x167/0x360 fs/ext4/super.c:7299
 write_blk fs/quota/quota_tree.c:70 [inline]
 get_free_dqblk+0x208/0x340 fs/quota/quota_tree.c:136
 do_insert_tree+0x19a/0x9b0 fs/quota/quota_tree.c:347
 do_insert_tree+0x753/0x9b0 fs/quota/quota_tree.c:402
 do_insert_tree+0x753/0x9b0 fs/quota/quota_tree.c:402
 do_insert_tree+0x731/0x9b0 fs/quota/quota_tree.c:402
 dq_insert_tree fs/quota/quota_tree.c:432 [inline]
 qtree_write_dquot+0x2cb/0x300 fs/quota/quota_tree.c:451
 v2_write_dquot+0xda/0x140 fs/quota/quota_v2.c:372
 dquot_acquire+0x1c0/0x2b0 fs/quota/dquot.c:470
 ext4_acquire_dquot+0x15f/0x200 fs/ext4/super.c:6931
 dqget+0x532/0x8d0 fs/quota/dquot.c:977
 __dquot_initialize+0x27f/0x7c0 fs/quota/dquot.c:1505
 dquot_initialize+0x1a/0x30 fs/quota/dquot.c:1567
 ext4_process_orphan+0x32/0x1c0 fs/ext4/orphan.c:329
 ext4_orphan_cleanup+0x6a8/0xa00 fs/ext4/orphan.c:474
 __ext4_fill_super fs/ext4/super.c:5607 [inline]
 ext4_fill_super+0x3171/0x34e0 fs/ext4/super.c:5726
 get_tree_bdev_flags+0x28e/0x300 fs/super.c:1636
 get_tree_bdev+0x1f/0x30 fs/super.c:1659
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5758
 vfs_get_tree+0x54/0x1d0 fs/super.c:1759
 do_new_mount+0x207/0x680 fs/namespace.c:3884
 path_mount+0x4a4/0xb20 fs/namespace.c:4211
 do_mount fs/namespace.c:4224 [inline]
 __do_sys_mount fs/namespace.c:4435 [inline]
 __se_sys_mount+0x28f/0x2e0 fs/namespace.c:4412
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4412
 x64_sys_call+0xd36/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff8687b1e0 of 16 bytes by task 25342 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:482 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1874 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1922 [inline]
 _prb_read_valid+0x1bc/0x920 kernel/printk/printk_ringbuffer.c:2113
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2185
 __console_flush_and_unlock kernel/printk/printk.c:3304 [inline]
 console_unlock+0x164/0x330 kernel/printk/printk.c:3325
 do_con_write+0x25c3/0x2630 drivers/tty/vt/vt.c:-1
 con_write+0x24/0x40 drivers/tty/vt/vt.c:3432
 process_output_block drivers/tty/n_tty.c:561 [inline]
 n_tty_write+0x7d8/0xb10 drivers/tty/n_tty.c:2377
 iterate_tty_write drivers/tty/tty_io.c:1015 [inline]
 file_tty_write+0x389/0x670 drivers/tty/tty_io.c:1090
 tty_write+0x25/0x30 drivers/tty/tty_io.c:1111
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0x49d/0x8d0 fs/read_write.c:684
 ksys_write+0xda/0x1a0 fs/read_write.c:736
 __do_sys_write fs/read_write.c:747 [inline]
 __se_sys_write fs/read_write.c:744 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:744
 x64_sys_call+0x2cdd/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 25342 Comm: syz.3.6941 Not tainted 6.15.0-rc4-syzkaller-00291-g2a239ffbebb5 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
==================================================================