loop2: detected capacity change from 0 to 1024
EXT4-fs: Ignoring removed mblk_io_submit option
EXT4-fs (loop2): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
==================================================================
BUG: KCSAN: data-race in data_push_tail / vsnprintf

write to 0xffffffff88bd6dad of 1 bytes by task 8121 on cpu 0:
 vsnprintf+0xdd8/0xe30
 va_format lib/vsprintf.c:1718 [inline]
 pointer+0x8a1/0xd20 lib/vsprintf.c:2479
 vsnprintf+0x861/0xe30 lib/vsprintf.c:2852
 vscnprintf+0x42/0x90 lib/vsprintf.c:2954
 printk_sprint+0x30/0x2d0 kernel/printk/printk.c:2216
 vprintk_store+0x589/0x870 kernel/printk/printk.c:2336
 vprintk_emit+0x15e/0x680 kernel/printk/printk.c:2408
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2447
 vprintk+0x75/0x80 kernel/printk/printk_safe.c:86
 _printk+0x7a/0xa0 kernel/printk/printk.c:2457
 __netdev_printk+0x2d1/0x3e0 net/core/dev.c:11940
 netdev_info+0x99/0xc0 net/core/dev.c:11987
 __dev_set_allmulti+0x15b/0x240 net/core/dev.c:8803
 dev_set_allmulti+0x1f/0x30 net/core/dev.c:8829
 packet_dev_mc net/packet/af_packet.c:3715 [inline]
 packet_dev_mclist_delete net/packet/af_packet.c:3737 [inline]
 packet_notifier+0x28d/0x510 net/packet/af_packet.c:4262
 notifier_call_chain kernel/notifier.c:93 [inline]
 raw_notifier_call_chain+0x6f/0x1d0 kernel/notifier.c:461
 call_netdevice_notifiers_info+0xae/0x100 net/core/dev.c:1996
 call_netdevice_notifiers_extack net/core/dev.c:2034 [inline]
 call_netdevice_notifiers net/core/dev.c:2048 [inline]
 unregister_netdevice_many_notify+0x8b7/0x11b0 net/core/dev.c:11520
 unregister_netdevice_many net/core/dev.c:11584 [inline]
 unregister_netdevice_queue+0x1f4/0x220 net/core/dev.c:11456
 br_dev_delete+0xc4/0xe0 net/bridge/br_if.c:396
 br_del_bridge+0x99/0xc0 net/bridge/br_if.c:495
 br_ioctl_stub+0x2fe/0x5d0
 br_ioctl_call net/socket.c:1182 [inline]
 sock_ioctl+0x433/0x640 net/socket.c:1282
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xc9/0x140 fs/ioctl.c:892
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:892
 x64_sys_call+0x1690/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff88bd6da8 of 8 bytes by task 8117 on cpu 1:
 data_make_reusable kernel/printk/printk_ringbuffer.c:594 [inline]
 data_push_tail+0x102/0x430 kernel/printk/printk_ringbuffer.c:679
 data_alloc+0xbe/0x2c0 kernel/printk/printk_ringbuffer.c:1054
 prb_reserve+0x85e/0xb60 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x558/0x870 kernel/printk/printk.c:2326
 vprintk_emit+0x15e/0x680 kernel/printk/printk.c:2408
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2447
 vprintk+0x75/0x80 kernel/printk/printk_safe.c:86
 _printk+0x7a/0xa0 kernel/printk/printk.c:2457
 __ext4_msg+0x18e/0x1a0 fs/ext4/super.c:998
 ext4_fill_super+0x980/0x3a10 fs/ext4/super.c:5748
 get_tree_bdev_flags+0x29f/0x310 fs/super.c:1636
 get_tree_bdev+0x1f/0x30 fs/super.c:1659
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5765
 vfs_get_tree+0x56/0x1e0 fs/super.c:1814
 do_new_mount+0x227/0x690 fs/namespace.c:3507
 path_mount+0x49b/0xb30 fs/namespace.c:3834
 do_mount fs/namespace.c:3847 [inline]
 __do_sys_mount fs/namespace.c:4057 [inline]
 __se_sys_mount+0x27c/0x2d0 fs/namespace.c:4034
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4034
 x64_sys_call+0x2c84/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000ffffe9d2 -> 0x0000000a65646564

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 8117 Comm: syz.2.1430 Not tainted 6.12.0-syzkaller-07834-g06afb0f36106 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
==================================================================