EXT4-fs warning (device loop0): ext4_end_bio:372: I/O error 10 writing to inode 18 starting block 61)
EXT4-fs warning (device loop0): ext4_end_bio:372: I/O error 10 writing to inode 18 starting block 125)
==================================================================
BUG: KCSAN: data-race in data_push_tail / vsnprintf

write to 0xffffffff88ed5ec0 of 2 bytes by task 21413 on cpu 0:
 vsnprintf+0x2ce/0x860 lib/vsprintf.c:2898
 vscnprintf+0x41/0x90 lib/vsprintf.c:3012
 printk_sprint+0x30/0x2d0 kernel/printk/printk.c:2192
 vprintk_store+0x568/0x830 kernel/printk/printk.c:2312
 vprintk_emit+0x15a/0x5c0 kernel/printk/printk.c:2402
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2441
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2451
 __netdev_printk+0x310/0x370 net/core/dev.c:12911
 netdev_info+0x9b/0xd0 net/core/dev.c:12958
 __dev_set_promiscuity+0x1fb/0x3f0 net/core/dev.c:9548
 netif_set_promiscuity+0x39/0x90 net/core/dev.c:9583
 dev_set_promiscuity+0xc1/0x170 net/core/dev_api.c:287
 nbp_delete_promisc net/bridge/br_if.c:254 [inline]
 del_nbp+0xc2/0x720 net/bridge/br_if.c:340
 br_dev_delete+0x4e/0xe0 net/bridge/br_if.c:386
 br_net_exit_rtnl+0x92/0xf0 net/bridge/br.c:414
 ops_exit_rtnl_list net/core/net_namespace.c:181 [inline]
 ops_undo_list+0x1b4/0x410 net/core/net_namespace.c:248
 cleanup_net+0x2f4/0x520 net/core/net_namespace.c:696
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3340
 worker_thread+0x582/0x770 kernel/workqueue.c:3421
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x149/0x290 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

read to 0xffffffff88ed5ec0 of 8 bytes by task 21991 on cpu 1:
 data_make_reusable kernel/printk/printk_ringbuffer.c:608 [inline]
 data_push_tail+0x100/0x470 kernel/printk/printk_ringbuffer.c:693
 data_alloc+0x11b/0x390 kernel/printk/printk_ringbuffer.c:1089
 prb_reserve+0x8d7/0xad0 kernel/printk/printk_ringbuffer.c:1724
 vprintk_store+0x53c/0x830 kernel/printk/printk.c:2302
 vprintk_emit+0x15a/0x5c0 kernel/printk/printk.c:2402
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2441
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2451
 __ext4_warning+0x12b/0x140 fs/ext4/super.c:1015
 ext4_end_bio+0xe9/0x380 fs/ext4/page-io.c:368
 bio_endio+0x37e/0x420 block/bio.c:1675
 submit_bio_noacct+0x76f/0x9a0 block/blk-core.c:886
 submit_bio+0x2a6/0x2c0 block/blk-core.c:921
 ext4_io_submit fs/ext4/page-io.c:404 [inline]
 io_submit_add_bh fs/ext4/page-io.c:445 [inline]
 ext4_bio_write_folio+0x6e8/0x9f0 fs/ext4/page-io.c:589
 mpage_submit_folio fs/ext4/inode.c:2087 [inline]
 mpage_process_page_bufs+0x4a1/0x620 fs/ext4/inode.c:2198
 mpage_prepare_extent_to_map+0x7a3/0xc20 fs/ext4/inode.c:2737
 ext4_do_writepages+0x6fe/0x27e0 fs/ext4/inode.c:2878
 ext4_writepages+0x179/0x300 fs/ext4/inode.c:3026
 do_writepages+0x1c6/0x310 mm/page-writeback.c:2598
 filemap_writeback mm/filemap.c:387 [inline]
 filemap_fdatawrite_range mm/filemap.c:412 [inline]
 file_write_and_wait_range+0x156/0x2c0 mm/filemap.c:786
 generic_buffers_fsync_noflush+0x45/0x130 fs/buffer.c:609
 ext4_fsync_nojournal fs/ext4/fsync.c:88 [inline]
 ext4_sync_file+0x1ab/0x690 fs/ext4/fsync.c:147
 vfs_fsync_range+0x10d/0x130 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2616 [inline]
 ext4_buffered_write_iter+0x34f/0x3c0 fs/ext4/file.c:305
 ext4_file_write_iter+0x387/0xf60 fs/ext4/file.c:-1
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x52a/0x960 fs/read_write.c:686
 ksys_write+0xda/0x1a0 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:746
 x64_sys_call+0x2847/0x3000 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000010000040b -> 0x6f7270207466656c

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 21991 Comm: syz.0.5138 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================
EXT4-fs warning (device loop0): ext4_end_bio:372: I/O error 10 writing to inode 18 starting block 161)
EXT4-fs warning (device loop0): ext4_end_bio:372: I/O error 10 writing to inode 18 starting block 201)
EXT4-fs (loop0): unmounting filesystem 00000000-0000-0000-0000-000000000000.