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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff866b4798 of 8 bytes by task 26631 on cpu 0:
 prb_reserve+0x740/0xb60
 vprintk_store+0x53f/0x810 kernel/printk/printk.c:2269
 vprintk_emit+0x13a/0x610 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_check_known_mac_addr+0x147/0x180 net/batman-adv/hard-interface.c:526
 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:1994
 call_netdevice_notifiers_extack net/core/dev.c:2032 [inline]
 call_netdevice_notifiers net/core/dev.c:2046 [inline]
 dev_set_mac_address+0x1ff/0x260 net/core/dev.c:9101
 dev_set_mac_address_user+0x31/0x50 net/core/dev.c:9115
 do_setlink+0x513/0x2490 net/core/rtnetlink.c:2855
 __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+0x599/0x670 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 0xffffffff866b4798 of 8 bytes by task 2951 on cpu 1:
 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+0x26f/0x760 kernel/printk/printk.c:1599
 do_syslog+0x393/0x7d0 kernel/printk/printk.c:1734
 __do_sys_syslog kernel/printk/printk.c:1826 [inline]
 __se_sys_syslog kernel/printk/printk.c:1824 [inline]
 __x64_sys_syslog+0x43/0x50 kernel/printk/printk.c:1824
 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: 0x00000000000005e1 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2951 Comm: klogd Not tainted 6.11.0-rc7-syzkaller-00039-g77f587896757 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
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