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

write to 0xffffffff86c6b670 of 8 bytes by task 8174 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_inode+0x2d9/0x3a0 fs/ext4/super.c:856
 __check_block_validity fs/ext4/inode.c:403 [inline]
 ext4_map_blocks+0x6cf/0x950 fs/ext4/inode.c:-1
 mpage_map_one_extent fs/ext4/inode.c:2397 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2491 [inline]
 ext4_do_writepages+0x161d/0x2720 fs/ext4/inode.c:2949
 ext4_writepages+0x18f/0x300 fs/ext4/inode.c:3043
 do_writepages+0x1b9/0x300 mm/page-writeback.c:2571
 __writeback_single_inode+0x7b/0x660 fs/fs-writeback.c:1787
 writeback_sb_inodes+0x4d9/0xaa0 fs/fs-writeback.c:2079
 wb_writeback+0x20c/0x510 fs/fs-writeback.c:2264
 wb_do_writeback fs/fs-writeback.c:2432 [inline]
 wb_workfn+0x1a4/0xa50 fs/fs-writeback.c:2477
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0x4d4/0x9a0 kernel/workqueue.c:3405
 worker_thread+0x569/0x750 kernel/workqueue.c:3486
 kthread+0x221/0x270 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffffffff86c6b670 of 8 bytes by task 16992 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_error_inode+0x298/0x3a0 fs/ext4/super.c:861
 ext4_free_branches+0x3b5/0x3f0 fs/ext4/indirect.c:1020
 ext4_ind_truncate+0x77c/0x840 fs/ext4/indirect.c:1201
 ext4_truncate+0x66a/0xa10 fs/ext4/inode.c:4670
 ext4_process_orphan+0x10b/0x1c0 fs/ext4/orphan.c:337
 ext4_orphan_cleanup+0x6a6/0xa10 fs/ext4/orphan.c:472
 __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:1634
 get_tree_bdev+0x1f/0x30 fs/super.c:1657
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5860
 vfs_get_tree+0x57/0x1d0 fs/super.c:1694
 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: 0xfffffffffffd43e0 -> 0x000000000009b520

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 16992 Comm: syz.2.4302 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================
EXT4-fs error (device loop2): ext4_free_branches:1023: inode #16: comm syz.2.4302: invalid indirect mapped block 83886080 (level 1)
loop2: lost file I/O error report for ino 16 type 5 pos 0x0 len 0x0 error -117
EXT4-fs (loop2): Remounting filesystem read-only
EXT4-fs (loop2): 1 orphan inode deleted
EXT4-fs (loop2): 1 truncate cleaned up
EXT4-fs (loop2): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback.
loop2: detected capacity change from 0 to 164
iso9660: Unknown parameter 'cruf00000000200'