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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff86ed4fd8 of 88 bytes by task 25977 on cpu 0:
 prb_reserve+0x6fb/0xaf0 kernel/printk/printk_ringbuffer.c:1693
 vprintk_store+0x54e/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x610 kernel/printk/printk.c:2455
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 printk_stack_address arch/x86/kernel/dumpstack.c:70 [inline]
 __show_trace_log_lvl+0x460/0x560 arch/x86/kernel/dumpstack.c:282
 __dump_stack+0x1d/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x95/0xd0 lib/dump_stack.c:120
 dump_stack+0x15/0x1b lib/dump_stack.c:129
 fail_dump lib/fault-inject.c:73 [inline]
 should_fail_ex+0x262/0x280 lib/fault-inject.c:174
 should_failslab+0x8c/0xb0 mm/failslab.c:46
 slab_pre_alloc_hook mm/slub.c:4638 [inline]
 slab_alloc_node mm/slub.c:4974 [inline]
 kmem_cache_alloc_noprof+0x7c/0x3f0 mm/slub.c:5010
 sk_prot_alloc+0x3f/0x180 net/core/sock.c:2245
 sk_alloc+0x34/0x3e0 net/core/sock.c:2307
 pn_socket_create+0x232/0x390 net/phonet/af_phonet.c:87
 __sock_create+0x2e5/0x580 net/socket.c:1676
 sock_create net/socket.c:1734 [inline]
 __sys_socket_create net/socket.c:1771 [inline]
 __sys_socket+0xaf/0x180 net/socket.c:1818
 __do_sys_socket net/socket.c:1832 [inline]
 __se_sys_socket net/socket.c:1830 [inline]
 __x64_sys_socket+0x3f/0x50 net/socket.c:1830
 x64_sys_call+0x246e/0x2550 arch/x86/include/generated/asm/syscalls_64.h:42
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86ed4fd8 of 8 bytes by task 25942 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:500 [inline]
 prb_first_seq kernel/printk/printk_ringbuffer.c:2017 [inline]
 _prb_read_valid+0x325/0x930 kernel/printk/printk_ringbuffer.c:2174
 prb_read_valid_info+0x7a/0xa0 kernel/printk/printk_ringbuffer.c:2280
 find_first_fitting_seq+0x1cc/0x330 kernel/printk/printk.c:1567
 syslog_print_all+0x11b/0x3c0 kernel/printk/printk.c:1699
 do_syslog+0x2fd/0x7f0 kernel/printk/printk.c:1777
 __do_sys_syslog kernel/printk/printk.c:1855 [inline]
 __se_sys_syslog kernel/printk/printk.c:1853 [inline]
 __x64_sys_syslog+0x41/0x50 kernel/printk/printk.c:1853
 x64_sys_call+0x1d36/0x2550 arch/x86/include/generated/asm/syscalls_64.h:104
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000002bc1 -> 0x0000000000004bc1

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 25942 Comm: syz.1.5467 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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