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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff868c90a0 of 88 bytes by task 30126 on cpu 0:
 prb_reserve+0x695/0xaf0 kernel/printk/printk_ringbuffer.c:1651
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2299
 vprintk_emit+0x10d/0x580 kernel/printk/printk.c:2399
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2438
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2448
 br_set_state+0x28c/0x390 net/bridge/br_stp.c:57
 br_stp_disable_port+0x5d/0x150 net/bridge/br_stp_if.c:106
 del_nbp+0xdc/0x790 net/bridge/br_if.c:343
 br_del_if+0x99/0x1e0 net/bridge/br_if.c:741
 br_del_slave+0x24/0x30 net/bridge/br_device.c:382
 do_set_master+0x227/0x460 net/core/rtnetlink.c:2940
 do_setlink+0xa43/0x2810 net/core/rtnetlink.c:3158
 rtnl_group_changelink net/core/rtnetlink.c:3783 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3937 [inline]
 rtnl_newlink+0xd8b/0x12d0 net/core/rtnetlink.c:4065
 rtnetlink_rcv_msg+0x5fe/0x6d0 net/core/rtnetlink.c:6951
 netlink_rcv_skb+0x123/0x220 net/netlink/af_netlink.c:2552
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6978
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x5c0/0x690 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x58b/0x6b0 net/netlink/af_netlink.c:1896
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x145/0x180 net/socket.c:742
 ____sys_sendmsg+0x31e/0x4e0 net/socket.c:2630
 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2684
 __sys_sendmsg net/socket.c:2716 [inline]
 __do_sys_sendmsg net/socket.c:2721 [inline]
 __se_sys_sendmsg net/socket.c:2719 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2719
 x64_sys_call+0x191e/0x3000 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff868c90a0 of 8 bytes by task 2992 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:483 [inline]
 prb_first_seq kernel/printk/printk_ringbuffer.c:1975 [inline]
 _prb_read_valid+0x383/0x920 kernel/printk/printk_ringbuffer.c:2132
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2203
 syslog_print+0xeb/0x540 kernel/printk/printk.c:1606
 do_syslog+0x52b/0x7e0 kernel/printk/printk.c:1758
 __do_sys_syslog kernel/printk/printk.c:1850 [inline]
 __se_sys_syslog kernel/printk/printk.c:1848 [inline]
 __x64_sys_syslog+0x41/0x50 kernel/printk/printk.c:1848
 x64_sys_call+0x2f45/0x3000 arch/x86/include/generated/asm/syscalls_64.h:104
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000000028e2 -> 0x00000000000048e2

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2992 Comm: klogd Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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