==================================================================
BUG: KCSAN: data-race in desc_read_finalized_seq / prb_reserve

write to 0xffffffff86935428 of 8 bytes by task 17116 on cpu 1:
 prb_reserve+0x750/0xb80 kernel/printk/printk_ringbuffer.c:-1
 vprintk_store+0x552/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x1a0/0x6c0 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x7f/0xb0 kernel/printk/printk.c:2475
 ib_get_eth_speed+0x327/0x4a0 drivers/infiniband/core/verbs.c:2006
 siw_query_port+0x38/0x2c0 drivers/infiniband/sw/siw/siw_verbs.c:179
 iw_query_port drivers/infiniband/core/device.c:2098 [inline]
 ib_query_port+0x36d/0x3b0 drivers/infiniband/core/device.c:2139
 ib_setup_port_attrs+0x14a/0x13c0 drivers/infiniband/core/sysfs.c:1429
 add_one_compat_dev+0x346/0x440 drivers/infiniband/core/device.c:968
 rdma_dev_init_net+0x18c/0x220 drivers/infiniband/core/device.c:1184
 ops_init+0x21e/0x2d0 net/core/net_namespace.c:138
 setup_net+0x14f/0x610 net/core/net_namespace.c:364
 copy_net_ns+0x5a3/0x740 net/core/net_namespace.c:518
 create_new_namespaces+0x228/0x430 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0xe6/0x120 kernel/nsproxy.c:228
 ksys_unshare+0x3d3/0x700 kernel/fork.c:3375
 __do_sys_unshare kernel/fork.c:3446 [inline]
 __se_sys_unshare kernel/fork.c:3444 [inline]
 __x64_sys_unshare+0x1f/0x30 kernel/fork.c:3444
 x64_sys_call+0x2c93/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:273
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86935428 of 8 bytes by task 17104 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:486 [inline]
 desc_read_finalized_seq+0x163/0x280 kernel/printk/printk_ringbuffer.c:1874
 prb_read kernel/printk/printk_ringbuffer.c:1922 [inline]
 _prb_read_valid+0x142/0x710 kernel/printk/printk_ringbuffer.c:2113
 prb_read_valid+0x42/0x70 kernel/printk/printk_ringbuffer.c:2185
 printk_get_next_message+0xdc/0x530 kernel/printk/printk.c:3005
 console_emit_next_record kernel/printk/printk.c:3092 [inline]
 console_flush_all+0x2a9/0x7a0 kernel/printk/printk.c:3226
 __console_flush_and_unlock kernel/printk/printk.c:3285 [inline]
 console_unlock+0xf4/0x350 kernel/printk/printk.c:3325
 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:561 [inline]
 n_tty_write+0x800/0xb20 drivers/tty/n_tty.c:2377
 iterate_tty_write drivers/tty/tty_io.c:1015 [inline]
 file_tty_write+0x382/0x6a0 drivers/tty/tty_io.c:1090
 tty_write+0x28/0x30 drivers/tty/tty_io.c:1111
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0x79b/0x950 fs/read_write.c:684
 ksys_write+0xeb/0x1b0 fs/read_write.c:736
 __do_sys_write fs/read_write.c:747 [inline]
 __se_sys_write fs/read_write.c:744 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:744
 x64_sys_call+0x2a45/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000001c4b -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 17104 Comm: syz.0.4971 Not tainted 6.15.0-rc1-syzkaller-00246-g900241a5cc15 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
==================================================================