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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff86cc10f0 of 88 bytes by task 25890 on cpu 0:
 prb_reserve+0x6fb/0xaf0 kernel/printk/printk_ringbuffer.c:1693
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x600 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
 __netdev_printk+0x310/0x370 net/core/dev.c:12966
 netdev_info+0xa6/0xd0 net/core/dev.c:13013
 __dev_set_promiscuity+0x1e5/0x3c0 net/core/dev.c:9614
 netif_set_promiscuity+0x39/0x90 net/core/dev.c:9641
 dev_set_promiscuity+0xb9/0x170 net/core/dev_api.c:288
 br_port_set_promisc net/bridge/br_if.c:109 [inline]
 br_manage_promisc+0xea/0x320 net/bridge/br_if.c:158
 nbp_update_port_count+0xc3/0xe0 net/bridge/br_if.c:243
 br_add_if+0x4fb/0xa60 net/bridge/br_if.c:630
 br_add_slave+0x2c/0x40 net/bridge/br_device.c:375
 do_set_master+0x37b/0x450 net/core/rtnetlink.c:3020
 do_setlink+0x976/0x2860 net/core/rtnetlink.c:3222
 rtnl_changelink net/core/rtnetlink.c:3849 [inline]
 __rtnl_newlink net/core/rtnetlink.c:4022 [inline]
 rtnl_newlink+0x1086/0x1400 net/core/rtnetlink.c:4159
 rtnetlink_rcv_msg+0x64b/0x720 net/core/rtnetlink.c:7076
 netlink_rcv_skb+0x11e/0x220 net/netlink/af_netlink.c:2556
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:7103
 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
 netlink_unicast+0x5a7/0x680 net/netlink/af_netlink.c:1345
 netlink_sendmsg+0x5be/0x6f0 net/netlink/af_netlink.c:1900
 sock_sendmsg_nosec net/socket.c:775 [inline]
 __sock_sendmsg net/socket.c:790 [inline]
 __sys_sendto+0x411/0x470 net/socket.c:2252
 __do_sys_sendto net/socket.c:2259 [inline]
 __se_sys_sendto net/socket.c:2255 [inline]
 __x64_sys_sendto+0x76/0x90 net/socket.c:2255
 x64_sys_call+0x2d35/0x3020 arch/x86/include/generated/asm/syscalls_64.h:45
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86cc10f0 of 8 bytes by task 2967 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:500 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1934 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1982 [inline]
 _prb_read_valid+0x18c/0x930 kernel/printk/printk_ringbuffer.c:2173
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2245
 syslog_print+0x109/0x560 kernel/printk/printk.c:1612
 do_syslog+0x52b/0x7f0 kernel/printk/printk.c:1763
 __do_sys_syslog kernel/printk/printk.c:1855 [inline]
 __se_sys_syslog kernel/printk/printk.c:1853 [inline]
 __x64_sys_syslog+0x41/0x50 kernel/printk/printk.c:1853
 x64_sys_call+0x2b9e/0x3020 arch/x86/include/generated/asm/syscalls_64.h:104
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000006824 -> 0x0000000000008824

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2967 Comm: klogd Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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