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BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff86882000 of 8 bytes by task 21191 on cpu 1:
 data_alloc+0x310/0x390 kernel/printk/printk_ringbuffer.c:1129
 prb_reserve+0x964/0xb60 kernel/printk/printk_ringbuffer.c:1724
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2302
 vprintk_emit+0x15a/0x610 kernel/printk/printk.c:2402
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2441
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2451
 siw_device_register drivers/infiniband/sw/siw/siw_main.c:73 [inline]
 siw_newlink+0x663/0x680 drivers/infiniband/sw/siw/siw_main.c:430
 nldev_newlink+0x369/0x3f0 drivers/infiniband/core/nldev.c:1797
 rdma_nl_rcv_msg drivers/infiniband/core/netlink.c:195 [inline]
 rdma_nl_rcv_skb drivers/infiniband/core/netlink.c:239 [inline]
 rdma_nl_rcv+0x47c/0x5a0 drivers/infiniband/core/netlink.c:259
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x5c0/0x690 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x58b/0x6b0 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x145/0x180 net/socket.c:742
 ____sys_sendmsg+0x31e/0x4a0 net/socket.c:2592
 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2681
 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 0xffffffff86882000 of 16 bytes by task 21185 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:496 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1931 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1979 [inline]
 _prb_read_valid+0x1bc/0x920 kernel/printk/printk_ringbuffer.c:2170
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2242
 __console_flush_and_unlock kernel/printk/printk.c:3338 [inline]
 console_unlock+0x164/0x2e0 kernel/printk/printk.c:3359
 class_console_lock_destructor include/linux/console.h:737 [inline]
 con_flush_chars+0xb2/0x1b0 drivers/tty/vt/vt.c:3636
 con_write+0x2e/0x40 drivers/tty/vt/vt.c:3566
 process_output_block drivers/tty/n_tty.c:557 [inline]
 n_tty_write+0x82d/0xbf0 drivers/tty/n_tty.c:2366
 iterate_tty_write drivers/tty/tty_io.c:1006 [inline]
 file_tty_write+0x378/0x690 drivers/tty/tty_io.c:1081
 tty_write+0x25/0x30 drivers/tty/tty_io.c:1102
 do_iter_readv_writev+0x4a1/0x540 fs/read_write.c:-1
 vfs_writev+0x2df/0x8b0 fs/read_write.c:1057
 do_writev+0xe7/0x210 fs/read_write.c:1103
 __do_sys_writev fs/read_write.c:1171 [inline]
 __se_sys_writev fs/read_write.c:1168 [inline]
 __x64_sys_writev+0x45/0x50 fs/read_write.c:1168
 x64_sys_call+0x1ba5/0x3000 arch/x86/include/generated/asm/syscalls_64.h:21
 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

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 21185 Comm: syz.7.4506 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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