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BUG: KCSAN: data-race in desc_read_finalized_seq / prb_reserve

write to 0xffffffff866b0808 of 8 bytes by task 19327 on cpu 0:
 prb_reserve+0x740/0xb60
 vprintk_store+0x558/0x870 kernel/printk/printk.c:2326
 vprintk_emit+0x168/0x690 kernel/printk/printk.c:2408
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2447
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x7a/0xa0 kernel/printk/printk.c:2457
 __netdev_printk+0x2d1/0x3e0 net/core/dev.c:12307
 netdev_info+0x99/0xc0 net/core/dev.c:12354
 __dev_set_promiscuity+0x165/0x340 net/core/dev.c:9046
 dev_set_promiscuity+0x3b/0x90 net/core/dev.c:9084
 br_port_set_promisc net/bridge/br_if.c:108 [inline]
 br_manage_promisc+0xf4/0x360 net/bridge/br_if.c:157
 nbp_update_port_count+0xbc/0xd0 net/bridge/br_if.c:242
 br_add_if+0x4f8/0xa50 net/bridge/br_if.c:640
 br_add_slave+0x2c/0x40 net/bridge/br_device.c:373
 do_set_master net/core/rtnetlink.c:2926 [inline]
 do_setlink+0x8f3/0x2370 net/core/rtnetlink.c:3125
 rtnl_changelink net/core/rtnetlink.c:3733 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3885 [inline]
 rtnl_newlink+0xde9/0x1250 net/core/rtnetlink.c:4022
 rtnetlink_rcv_msg+0x651/0x710 net/core/rtnetlink.c:6912
 netlink_rcv_skb+0x12c/0x230 net/netlink/af_netlink.c:2533
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6939
 netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline]
 netlink_unicast+0x599/0x670 net/netlink/af_netlink.c:1338
 netlink_sendmsg+0x5cc/0x6e0 net/netlink/af_netlink.c:1882
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg+0x140/0x180 net/socket.c:733
 __sys_sendto+0x1a8/0x230 net/socket.c:2187
 __do_sys_sendto net/socket.c:2194 [inline]
 __se_sys_sendto net/socket.c:2190 [inline]
 __x64_sys_sendto+0x78/0x90 net/socket.c:2190
 x64_sys_call+0x29fa/0x2dc0 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 0xffffffff866b0808 of 8 bytes by task 19353 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:486 [inline]
 desc_read_finalized_seq+0x157/0x280 kernel/printk/printk_ringbuffer.c:1874
 prb_read kernel/printk/printk_ringbuffer.c:1922 [inline]
 _prb_read_valid+0x140/0x6c0 kernel/printk/printk_ringbuffer.c:2113
 prb_read_valid+0x3d/0x60 kernel/printk/printk_ringbuffer.c:2182
 __console_flush_and_unlock kernel/printk/printk.c:3288 [inline]
 console_unlock+0x180/0x340 kernel/printk/printk.c:3309
 con_flush_chars+0xb0/0x1b0 drivers/tty/vt/vt.c:3503
 con_write+0x30/0x40 drivers/tty/vt/vt.c:3433
 process_output_block drivers/tty/n_tty.c:574 [inline]
 n_tty_write+0x843/0xb80 drivers/tty/n_tty.c:2389
 iterate_tty_write drivers/tty/tty_io.c:1015 [inline]
 file_tty_write+0x37a/0x680 drivers/tty/tty_io.c:1090
 tty_write+0x28/0x30 drivers/tty/tty_io.c:1111
 new_sync_write fs/read_write.c:586 [inline]
 vfs_write+0x77b/0x920 fs/read_write.c:679
 ksys_write+0xe8/0x1b0 fs/read_write.c:731
 __do_sys_write fs/read_write.c:742 [inline]
 __se_sys_write fs/read_write.c:739 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:739
 x64_sys_call+0x287e/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:2
 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: 0x00000000000064ed -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 19353 Comm: syz.2.23770 Tainted: G        W          6.14.0-rc7-syzkaller-00205-g586de92313fc #0
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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