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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff8690baa8 of 88 bytes by task 29701 on cpu 1:
 prb_reserve+0x76a/0xb60 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
 __netdev_printk+0x310/0x370 net/core/dev.c:12724
 netdev_info+0x9b/0xd0 net/core/dev.c:12771
 netif_set_allmulti+0x14c/0x220 net/core/dev.c:9516
 dev_set_allmulti+0xcc/0x170 net/core/dev_api.c:313
 macsec_dev_change_rx_flags+0xa8/0x110 drivers/net/macsec.c:3644
 dev_change_rx_flags net/core/dev.c:9420 [inline]
 netif_set_allmulti+0x181/0x220 net/core/dev.c:9518
 dev_set_allmulti+0xcc/0x170 net/core/dev_api.c:313
 br_add_if+0x43f/0xa60 net/bridge/br_if.c:722
 br_add_slave+0x2c/0x40 net/bridge/br_device.c:375
 do_set_master+0x390/0x460 net/core/rtnetlink.c:2956
 rtnl_newlink_create+0x426/0x620 net/core/rtnetlink.c:3847
 __rtnl_newlink net/core/rtnetlink.c:3950 [inline]
 rtnl_newlink+0xf5b/0x1360 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:718 [inline]
 __sock_sendmsg+0x145/0x180 net/socket.c:733
 ____sys_sendmsg+0x31e/0x4a0 net/socket.c:2608
 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2662
 __sys_sendmsg net/socket.c:2694 [inline]
 __do_sys_sendmsg net/socket.c:2699 [inline]
 __se_sys_sendmsg net/socket.c:2697 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2697
 x64_sys_call+0x17ba/0x3000 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff8690baa8 of 8 bytes by task 2995 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:483 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1892 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1940 [inline]
 _prb_read_valid+0x1c4/0x920 kernel/printk/printk_ringbuffer.c:2131
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2203
 syslog_print+0x23a/0x540 kernel/printk/printk.c:1623
 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+0x27ce/0x3000 arch/x86/include/generated/asm/syscalls_64.h:104
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000000034fd -> 0x00000000000054fd

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2995 Comm: klogd Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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