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

write to 0xffffffff86e64d30 of 8 bytes by task 13155 on cpu 1:
 data_alloc+0x308/0x380 kernel/printk/printk_ringbuffer.c:1129
 prb_reserve+0x8e3/0xaf0 kernel/printk/printk_ringbuffer.c:1725
 vprintk_store+0x54e/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x580 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
 batadv_hardif_deactivate_interface net/batman-adv/hard-interface.c:781 [inline]
 batadv_hardif_disable_interface+0x106/0x780 net/batman-adv/hard-interface.c:909
 batadv_meshif_destroy_netlink+0x41/0x80 net/batman-adv/mesh-interface.c:1173
 rtnl_delete_link net/core/rtnetlink.c:3688 [inline]
 rtnl_dellink+0x424/0x630 net/core/rtnetlink.c:3731
 rtnetlink_rcv_msg+0x64b/0x720 net/core/rtnetlink.c:7169
 netlink_rcv_skb+0x11e/0x220 net/netlink/af_netlink.c:2584
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:7196
 netlink_unicast_kernel net/netlink/af_netlink.c:1335 [inline]
 netlink_unicast+0x665/0x740 net/netlink/af_netlink.c:1361
 netlink_sendmsg+0x5ef/0x740 net/netlink/af_netlink.c:1920
 sock_sendmsg_nosec net/socket.c:800 [inline]
 __sock_sendmsg net/socket.c:818 [inline]
 ____sys_sendmsg+0x54a/0x590 net/socket.c:2715
 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2769
 __sys_sendmsg net/socket.c:2801 [inline]
 __do_sys_sendmsg net/socket.c:2806 [inline]
 __se_sys_sendmsg net/socket.c:2804 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2804
 x64_sys_call+0x22ab/0x2550 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86e64d30 of 8 bytes by task 13161 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:495 [inline]
 desc_push_tail kernel/printk/printk_ringbuffer.c:791 [inline]
 desc_reserve kernel/printk/printk_ringbuffer.c:937 [inline]
 prb_reserve+0x21a/0xaf0 kernel/printk/printk_ringbuffer.c:1675
 vprintk_store+0x54e/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x580 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_setup_super+0x572/0x580 fs/ext4/super.c:3213
 __ext4_fill_super fs/ext4/super.c:5686 [inline]
 ext4_fill_super+0x29e2/0x37d0 fs/ext4/super.c:5899
 get_tree_bdev_flags+0x297/0x300 fs/super.c:1821
 get_tree_bdev+0x1f/0x30 fs/super.c:1844
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5931
 vfs_get_tree+0x57/0x1d0 fs/super.c:1881
 fc_mount fs/namespace.c:1282 [inline]
 do_new_mount_fc fs/namespace.c:3910 [inline]
 do_new_mount+0x288/0x730 fs/namespace.c:3986
 path_mount+0x4ad/0xba0 fs/namespace.c:4337
 do_mount fs/namespace.c:4350 [inline]
 __do_sys_mount fs/namespace.c:4565 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4542
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4542
 x64_sys_call+0xc3b/0x2550 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xfffffffffffc3e08 -> 0x00000000000675c0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 13161 Comm: syz.1.2047 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/15/2026
==================================================================
[EXT4 FS bs=1024, gc=1, bpg=8192, ipg=32, mo=a840c018, mo2=0082]
System zones: 2-12, 7-7
EXT4-fs error (device loop1): ext4_orphan_get:1404: inode #17: comm syz.1.2047: iget: immutable or append flags not allowed on symlinks
loop1: lost file I/O error report for ino 17 type 5 pos 0x0 len 0x0 error -117
EXT4-fs error (device loop1): ext4_orphan_get:1409: comm syz.1.2047: couldn't read orphan inode 17 (err -117)
loop1: lost filesystem error report for type 5 error -117
EXT4-fs (loop1): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.