EXT4-fs error (device loop6): ext4_validate_block_bitmap:432: comm syz.6.8947: bg 0: block 5: invalid block bitmap
==================================================================
BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff86c8b6c8 of 8 bytes by task 29803 on cpu 1:
 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+0x298/0x3a0 fs/ext4/super.c:861
 ext4_do_update_inode fs/ext4/inode.c:5742 [inline]
 ext4_mark_iloc_dirty+0x359/0xd00 fs/ext4/inode.c:6404
 ext4_orphan_del+0x698/0x6c0 fs/ext4/orphan.c:301
 ext4_truncate+0x812/0xa10 fs/ext4/inode.c:4688
 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

read to 0xffffffff86c8b6c8 of 8 bytes by task 29795 on cpu 0:
 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_msg+0x1aa/0x1c0 fs/ext4/super.c:1001
 mpage_map_and_submit_extent fs/ext4/inode.c:2516 [inline]
 ext4_do_writepages+0x1d14/0x2720 fs/ext4/inode.c:2949
 ext4_writepages+0x18f/0x300 fs/ext4/inode.c:3043
 do_writepages+0x1b9/0x300 mm/page-writeback.c:2571
 filemap_writeback mm/filemap.c:387 [inline]
 filemap_fdatawrite_range mm/filemap.c:412 [inline]
 file_write_and_wait_range+0x178/0x2f0 mm/filemap.c:786
 mmb_fsync_noflush+0x48/0x140 fs/buffer.c:652
 ext4_fsync_nojournal fs/ext4/fsync.c:92 [inline]
 ext4_sync_file+0x1f2/0x6d0 fs/ext4/fsync.c:160
 vfs_fsync_range fs/sync.c:186 [inline]
 vfs_fsync fs/sync.c:200 [inline]
 do_fsync fs/sync.c:211 [inline]
 __do_sys_fdatasync fs/sync.c:221 [inline]
 __se_sys_fdatasync fs/sync.c:219 [inline]
 __x64_sys_fdatasync+0x83/0xe0 fs/sync.c:219
 x64_sys_call+0x2d1f/0x3020 arch/x86/include/generated/asm/syscalls_64.h:76
 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: 0x00000000001050b0 -> 0x00000000001b26c8

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 29795 Comm: syz.6.8947 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================
EXT4-fs (loop6): Delayed block allocation failed for inode 18 at logical offset 0 with max blocks 284 with error 28
EXT4-fs (loop6): This should not happen!! Data will be lost

EXT4-fs (loop6): Total free blocks count 0
EXT4-fs (loop6): Free/Dirty block details
EXT4-fs (loop6): free_blocks=0
EXT4-fs (loop6): dirty_blocks=288
EXT4-fs (loop6): Block reservation details
EXT4-fs (loop6): i_reserved_data_blocks=288
EXT4-fs (loop6): shut down requested (0)