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BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff86c88960 of 8 bytes by task 3306 on cpu 0:
 data_alloc+0x2fc/0x380 kernel/printk/printk_ringbuffer.c:1129
 prb_reserve+0x8e3/0xaf0 kernel/printk/printk_ringbuffer.c:1727
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x600 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+0x25e/0x270 lib/fault-inject.c:174
 should_failslab+0x8c/0xb0 mm/failslab.c:46
 slab_pre_alloc_hook mm/slub.c:4539 [inline]
 slab_alloc_node mm/slub.c:4897 [inline]
 kmem_cache_alloc_noprof+0x7f/0x3c0 mm/slub.c:4931
 alloc_filename fs/namei.c:147 [inline]
 do_getname+0x2e/0x1c0 fs/namei.c:187
 getname_flags fs/namei.c:230 [inline]
 class_filename_flags_constructor include/linux/fs.h:2566 [inline]
 user_path_at+0x28/0x100 fs/namei.c:3640
 ksys_umount fs/namespace.c:2067 [inline]
 __do_sys_umount fs/namespace.c:2075 [inline]
 __se_sys_umount fs/namespace.c:2073 [inline]
 __x64_sys_umount+0x85/0xe0 fs/namespace.c:2073
 x64_sys_call+0x103b/0x3020 arch/x86/include/generated/asm/syscalls_64.h:167
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86c88960 of 16 bytes by task 4690 on cpu 1:
 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
 printk_get_next_message+0xea/0x550 kernel/printk/printk.c:3052
 console_emit_next_record kernel/printk/printk.c:3137 [inline]
 console_flush_one_record kernel/printk/printk.c:3269 [inline]
 console_flush_all+0x2bc/0x6b0 kernel/printk/printk.c:3343
 __console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
 console_unlock+0xa1/0x280 kernel/printk/printk.c:3413
 vprintk_emit+0x3e4/0x600 kernel/printk/printk.c:2479
 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
 fail_dump lib/fault-inject.c:66 [inline]
 should_fail_ex+0x246/0x270 lib/fault-inject.c:174
 should_failslab+0x8c/0xb0 mm/failslab.c:46
 slab_pre_alloc_hook mm/slub.c:4539 [inline]
 slab_alloc_node mm/slub.c:4897 [inline]
 kmem_cache_alloc_node_noprof+0x85/0x3d0 mm/slub.c:4989
 __alloc_skb+0x2db/0x6f0 net/core/skbuff.c:704
 alloc_skb include/linux/skbuff.h:1384 [inline]
 nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:819 [inline]
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:876 [inline]
 nsim_dev_trap_report_work+0x18b/0x630 drivers/net/netdevsim/dev.c:922
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0x4d4/0x9a0 kernel/workqueue.c:3405
 worker_thread+0x569/0x750 kernel/workqueue.c:3486
 kthread+0x221/0x270 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 4690 Comm: kworker/u8:51 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: events_unbound nsim_dev_trap_report_work

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