loop6: detected capacity change from 0 to 128
==================================================================
BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff868754e0 of 8 bytes by task 22043 on cpu 0:
 data_alloc+0x290/0x2c0 kernel/printk/printk_ringbuffer.c:1096
 prb_reserve+0x86a/0xb80 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x552/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x1a0/0x6c0 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x7f/0xb0 kernel/printk/printk.c:2475
 __netdev_printk+0x2d1/0x3e0 net/core/dev.c:12411
 netdev_info+0x9e/0xd0 net/core/dev.c:12458
 netif_set_allmulti+0x15f/0x250 net/core/dev.c:9245
 dev_set_allmulti+0xd4/0x190 net/core/dev_api.c:289
 nbp_delete_promisc net/bridge/br_if.c:252 [inline]
 del_nbp+0x68/0x770 net/bridge/br_if.c:340
 br_dev_delete+0x4e/0xe0 net/bridge/br_if.c:386
 br_net_exit_batch_rtnl+0xca/0x170 net/bridge/br.c:376
 cleanup_net+0x400/0x8a0 net/core/net_namespace.c:647
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4de/0xa20 kernel/workqueue.c:3319
 worker_thread+0x52c/0x710 kernel/workqueue.c:3400
 kthread+0x4b7/0x540 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffffffff868754e0 of 8 bytes by task 24587 on cpu 1:
 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+0x239/0xb80 kernel/printk/printk_ringbuffer.c:1619
 vprintk_store+0x552/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x1a0/0x6c0 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x7f/0xb0 kernel/printk/printk.c:2475
 bio_check_eod block/blk-core.c:563 [inline]
 submit_bio_noacct+0x82e/0x930 block/blk-core.c:796
 submit_bio+0x218/0x230 block/blk-core.c:916
 dio_bio_submit fs/direct-io.c:442 [inline]
 __blockdev_direct_IO+0x191f/0x1ef0 fs/direct-io.c:1270
 blockdev_direct_IO include/linux/fs.h:3422 [inline]
 fat_direct_IO+0x10a/0x1d0 fs/fat/inode.c:281
 generic_file_direct_write+0xf9/0x250 mm/filemap.c:4037
 __generic_file_write_iter+0xae/0x120 mm/filemap.c:4206
 generic_file_write_iter+0x92/0x310 mm/filemap.c:4246
 aio_write+0x324/0x460 fs/aio.c:1633
 __io_submit_one fs/aio.c:-1 [inline]
 io_submit_one+0xb0c/0x1230 fs/aio.c:2052
 __do_sys_io_submit fs/aio.c:2111 [inline]
 __se_sys_io_submit+0xf7/0x280 fs/aio.c:2081
 __x64_sys_io_submit+0x43/0x50 fs/aio.c:2081
 x64_sys_call+0xa8b/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:210
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000000929a0 -> 0x0000000000138b08

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 24587 Comm: syz.6.6770 Not tainted 6.15.0-rc3-syzkaller-00001-g9d7a0577c9db #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
==================================================================
syz.6.6770: attempt to access beyond end of device
loop6: rw=34817, sector=97, nr_sectors = 32 limit=128