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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff866af3c8 of 8 bytes by task 21397 on cpu 1:
 prb_reserve+0x740/0xb60
 vprintk_store+0x53f/0x810 kernel/printk/printk.c:2301
 vprintk_emit+0x15e/0x680 kernel/printk/printk.c:2383
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2422
 vprintk+0x75/0x80 kernel/printk/printk_safe.c:68
 _printk+0x7a/0xa0 kernel/printk/printk.c:2432
 batadv_check_known_mac_addr+0x153/0x180 net/batman-adv/hard-interface.c:528
 batadv_hard_if_event+0x4b0/0x1010 net/batman-adv/hard-interface.c:998
 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]
 dev_set_mac_address+0x1ff/0x260 net/core/dev.c:9108
 dev_set_mac_address_user+0x31/0x50 net/core/dev.c:9122
 do_setlink+0x513/0x2490 net/core/rtnetlink.c:2884
 __rtnl_newlink net/core/rtnetlink.c:3725 [inline]
 rtnl_newlink+0x11a3/0x1690 net/core/rtnetlink.c:3772
 rtnetlink_rcv_msg+0x6aa/0x710 net/core/rtnetlink.c:6675
 netlink_rcv_skb+0x12c/0x230 net/netlink/af_netlink.c:2551
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6693
 netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
 netlink_unicast+0x599/0x670 net/netlink/af_netlink.c:1357
 netlink_sendmsg+0x5cc/0x6e0 net/netlink/af_netlink.c:1901
 sock_sendmsg_nosec net/socket.c:729 [inline]
 __sock_sendmsg+0x140/0x180 net/socket.c:744
 __sys_sendto+0x1d6/0x260 net/socket.c:2214
 __do_sys_sendto net/socket.c:2226 [inline]
 __se_sys_sendto net/socket.c:2222 [inline]
 __x64_sys_sendto+0x78/0x90 net/socket.c:2222
 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 0xffffffff866af3c8 of 8 bytes by task 3007 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:486 [inline]
 prb_first_seq kernel/printk/printk_ringbuffer.c:1957 [inline]
 _prb_read_valid+0x3bb/0xba0 kernel/printk/printk_ringbuffer.c:2114
 prb_read_valid+0x3d/0x60 kernel/printk/printk_ringbuffer.c:2182
 syslog_print+0xfc/0x760 kernel/printk/printk.c:1614
 do_syslog+0x397/0x7e0 kernel/printk/printk.c:1766
 __do_sys_syslog kernel/printk/printk.c:1858 [inline]
 __se_sys_syslog kernel/printk/printk.c:1856 [inline]
 __x64_sys_syslog+0x43/0x50 kernel/printk/printk.c:1856
 x64_sys_call+0x1677/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:104
 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: 0x00000000000024ef -> 0x00000000000044ef

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3007 Comm: klogd Not tainted 6.12.0-rc7-syzkaller-00070-g0a9b9d17f3a7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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