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BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff86e751a8 of 8 bytes by task 17167 on cpu 1:
 data_alloc+0x2fc/0x380 kernel/printk/printk_ringbuffer.c:1129
 prb_reserve+0x8e3/0xaf0 kernel/printk/printk_ringbuffer.c:1727
 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
 show_opcodes+0xfd/0x120 arch/x86/kernel/dumpstack.c:121
 show_iret_regs+0x12/0x40 arch/x86/kernel/dumpstack.c:147
 __show_regs+0x2a/0x430 arch/x86/kernel/process_64.c:78
 show_regs_if_on_stack arch/x86/kernel/dumpstack.c:165 [inline]
 __show_trace_log_lvl+0x38f/0x560 arch/x86/kernel/dumpstack.c:298
 __warn+0x159/0x330 kernel/panic.c:1104
 __report_bug+0x19b/0x490 lib/bug.c:254
 report_bug+0x9b/0xe0 lib/bug.c:286
 handle_bug+0x9c/0x200 arch/x86/kernel/traps.c:436
 exc_invalid_op+0x1a/0x50 arch/x86/kernel/traps.c:490
 asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:593
 __skb_set_length include/linux/skbuff.h:3337 [inline]
 __skb_trim include/linux/skbuff.h:3345 [inline]
 skb_trim+0xb4/0xc0 net/core/skbuff.c:2717
 sctp_ulpevent_make_rcvmsg+0x298/0x410 net/sctp/ulpevent.c:728
 sctp_ulpq_tail_data+0x5a/0x5d0 net/sctp/ulpqueue.c:90
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1477 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1211 [inline]
 sctp_do_sm+0x1328/0x33b0 net/sctp/sm_sideeffect.c:1182
 sctp_assoc_bh_rcv+0x2a7/0x450 net/sctp/associola.c:1048
 sctp_inq_push+0x152/0x160 net/sctp/inqueue.c:91
 sctp_backlog_rcv+0xe4/0x490 net/sctp/input.c:331
 sk_backlog_rcv include/net/sock.h:1192 [inline]
 __release_sock+0x131/0x2b0 net/core/sock.c:3298
 release_sock+0x125/0x180 net/core/sock.c:3897
 sctp_sendmsg+0x1516/0x1d00 net/sctp/socket.c:2053
 inet_sendmsg+0xc5/0xd0 net/ipv4/af_inet.c:865
 sock_sendmsg_nosec net/socket.c:801 [inline]
 __sock_sendmsg net/socket.c:815 [inline]
 sock_write_iter+0x2a4/0x2f0 net/socket.c:1266
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x57a/0x990 fs/read_write.c:687
 ksys_write+0xdc/0x1a0 fs/read_write.c:739
 __do_sys_write fs/read_write.c:750 [inline]
 __se_sys_write fs/read_write.c:747 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:747
 x64_sys_call+0x154e/0x2550 arch/x86/include/generated/asm/syscalls_64.h:2
 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 0xffffffff86e751a8 of 16 bytes by task 2962 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:496 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1934 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1982 [inline]
 _prb_read_valid+0x183/0x930 kernel/printk/printk_ringbuffer.c:2173
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2245
 syslog_print+0x253/0x550 kernel/printk/printk.c:1628
 do_syslog+0x52b/0x7f0 kernel/printk/printk.c:1763
 __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

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2962 Comm: klogd Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
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