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

write to 0xffffffff86666188 of 8 bytes by task 10825 on cpu 1:
 data_alloc+0x291/0x2c0 kernel/printk/printk_ringbuffer.c:1096
 prb_reserve+0x85e/0xb60 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x53f/0x810 kernel/printk/printk.c:2269
 vprintk_emit+0x10c/0x5e0 kernel/printk/printk.c:2329
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2363
 vprintk+0x75/0x80 kernel/printk/printk_safe.c:45
 _printk+0x7a/0xa0 kernel/printk/printk.c:2373
 batadv_hardif_activate_interface+0x1e5/0x330 net/batman-adv/hard-interface.c:675
 batadv_hard_if_event+0x47a/0x1000 net/batman-adv/hard-interface.c:977
 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:1994
 __dev_notify_flags+0xff/0x1a0
 dev_change_flags+0xab/0xd0 net/core/dev.c:8915
 do_setlink+0x841/0x2490 net/core/rtnetlink.c:2900
 __rtnl_newlink net/core/rtnetlink.c:3696 [inline]
 rtnl_newlink+0x11a3/0x1690 net/core/rtnetlink.c:3743
 rtnetlink_rcv_msg+0x6aa/0x710 net/core/rtnetlink.c:6647
 netlink_rcv_skb+0x12c/0x230 net/netlink/af_netlink.c:2550
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6665
 netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
 netlink_unicast+0x593/0x670 net/netlink/af_netlink.c:1357
 netlink_sendmsg+0x5cc/0x6e0 net/netlink/af_netlink.c:1901
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x140/0x180 net/socket.c:745
 __sys_sendto+0x1e5/0x260 net/socket.c:2204
 __do_sys_sendto net/socket.c:2216 [inline]
 __se_sys_sendto net/socket.c:2212 [inline]
 __x64_sys_sendto+0x78/0x90 net/socket.c:2212
 x64_sys_call+0x2959/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:45
 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 0xffffffff86666188 of 8 bytes by task 11038 on cpu 0:
 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+0x235/0xb60 kernel/printk/printk_ringbuffer.c:1619
 vprintk_store+0x53f/0x810 kernel/printk/printk.c:2269
 vprintk_emit+0x10c/0x5e0 kernel/printk/printk.c:2329
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2363
 vprintk+0x75/0x80 kernel/printk/printk_safe.c:45
 _printk+0x7a/0xa0 kernel/printk/printk.c:2373
 __ext4_msg+0x18e/0x1a0 fs/ext4/super.c:990
 ext4_fill_super+0x980/0x39e0 fs/ext4/super.c:5679
 get_tree_bdev+0x256/0x2e0 fs/super.c:1635
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5696
 vfs_get_tree+0x56/0x1d0 fs/super.c:1800
 do_new_mount+0x227/0x690 fs/namespace.c:3472
 path_mount+0x49b/0xb30 fs/namespace.c:3799
 do_mount fs/namespace.c:3812 [inline]
 __do_sys_mount fs/namespace.c:4020 [inline]
 __se_sys_mount+0x27c/0x2d0 fs/namespace.c:3997
 __x64_sys_mount+0x67/0x80 fs/namespace.c:3997
 x64_sys_call+0x203e/0x2d60 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: 0xfffffffffffc77a8 -> 0x00000000000743e0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 11038 Comm: syz.0.1776 Tainted: G        W          6.11.0-rc2-syzkaller #0
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
==================================================================
EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
EXT4-fs error (device loop0): ext4_mb_generate_buddy:1220: group 0, block bitmap and bg descriptor inconsistent: 25 vs 150994969 free clusters
EXT4-fs (loop0): Delayed block allocation failed for inode 18 at logical offset 0 with max blocks 4 with error 28
EXT4-fs (loop0): This should not happen!! Data will be lost

EXT4-fs (loop0): Total free blocks count 0
EXT4-fs (loop0): Free/Dirty block details
EXT4-fs (loop0): free_blocks=2415919104
EXT4-fs (loop0): dirty_blocks=16
EXT4-fs (loop0): Block reservation details
EXT4-fs (loop0): i_reserved_data_blocks=1