syzbot

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BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff86063820 of 8 bytes by task 15366 on cpu 0:
 data_alloc+0x291/0x2c0 kernel/printk/printk_ringbuffer.c:1096
 prb_reserve+0x85e/0xb60 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x53f/0x810 kernel/printk/printk.c:2269
 vprintk_emit+0x10c/0x5e0 kernel/printk/printk.c:2329
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2363
 vprintk+0x75/0x80 kernel/printk/printk_safe.c:45
 _printk+0x7a/0xa0 kernel/printk/printk.c:2373
 ib_get_eth_speed+0x322/0x4a0 drivers/infiniband/core/verbs.c:1994
 rxe_query_port+0x64/0x160 drivers/infiniband/sw/rxe/rxe_verbs.c:55
 __ib_query_port drivers/infiniband/core/device.c:2067 [inline]
 ib_query_port+0x115/0x3a0 drivers/infiniband/core/device.c:2099
 ib_setup_port_attrs+0x148/0x1340 drivers/infiniband/core/sysfs.c:1440
 add_one_compat_dev+0x2e6/0x3e0 drivers/infiniband/core/device.c:969
 rdma_dev_init_net+0x183/0x210 drivers/infiniband/core/device.c:1185
 ops_init+0x201/0x2d0 net/core/net_namespace.c:136
 setup_net+0x2ea/0x7c0 net/core/net_namespace.c:340
 copy_net_ns+0x389/0x520 net/core/net_namespace.c:505
 create_new_namespaces+0x228/0x430 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0xe6/0x120 kernel/nsproxy.c:228
 ksys_unshare+0x3da/0x720 kernel/fork.c:3323
 __do_sys_unshare kernel/fork.c:3394 [inline]
 __se_sys_unshare kernel/fork.c:3392 [inline]
 __x64_sys_unshare+0x1f/0x30 kernel/fork.c:3392
 x64_sys_call+0x21e5/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:273
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86063820 of 8 bytes by task 15369 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:482 [inline]
 desc_push_tail kernel/printk/printk_ringbuffer.c:778 [inline]
 desc_reserve kernel/printk/printk_ringbuffer.c:924 [inline]
 prb_reserve+0x235/0xb60 kernel/printk/printk_ringbuffer.c:1619
 vprintk_store+0x53f/0x810 kernel/printk/printk.c:2269
 vprintk_emit+0x10c/0x5e0 kernel/printk/printk.c:2329
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2363
 vprintk+0x75/0x80 kernel/printk/printk_safe.c:45
 _printk+0x7a/0xa0 kernel/printk/printk.c:2373
 sync_thread_backup+0xa5/0x12f0 net/netfilter/ipvs/ip_vs_sync.c:1710
 kthread+0x1d1/0x210 kernel/kthread.c:388
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0xfffffffffffc1910 -> 0x000000000006cfa8

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 15369 Comm: ipvs-b:9:0 Not tainted 6.9.0-rc6-syzkaller-00232-gddb4c3f25b7b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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IPVS: sync thread started: state = BACKUP, mcast_ifn = netdevsim0, syncid = 0, id = 0