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BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff8688ea30 of 8 bytes by task 20047 on cpu 1:
 data_alloc+0x271/0x2b0 kernel/printk/printk_ringbuffer.c:1095
 prb_reserve+0x808/0xaf0 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2475
 rock_check_overflow+0x19c/0x1c0 fs/isofs/rock.c:186
 get_rock_ridge_filename+0x1df/0x5b0 fs/isofs/rock.c:228
 isofs_find_entry fs/isofs/namei.c:110 [inline]
 isofs_lookup+0x3c4/0x930 fs/isofs/namei.c:165
 lookup_open fs/namei.c:3695 [inline]
 open_last_lookups fs/namei.c:3816 [inline]
 path_openat+0xcf0/0x2170 fs/namei.c:4052
 do_filp_open+0x109/0x230 fs/namei.c:4082
 do_sys_openat2+0xa6/0x110 fs/open.c:1437
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_open fs/open.c:1460 [inline]
 __se_sys_open fs/open.c:1456 [inline]
 __x64_sys_open+0xe6/0x110 fs/open.c:1456
 x64_sys_call+0x14d4/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:3
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff8688ea30 of 16 bytes by task 20044 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:482 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1874 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1922 [inline]
 _prb_read_valid+0x1bc/0x920 kernel/printk/printk_ringbuffer.c:2113
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2185
 printk_get_next_message+0xc8/0x510 kernel/printk/printk.c:3005
 console_emit_next_record kernel/printk/printk.c:3092 [inline]
 console_flush_all+0x290/0x730 kernel/printk/printk.c:3226
 __console_flush_and_unlock kernel/printk/printk.c:3285 [inline]
 console_unlock+0xa1/0x330 kernel/printk/printk.c:3325
 do_con_write+0x28d7/0x2940 drivers/tty/vt/vt.c:-1
 con_write+0x24/0x40 drivers/tty/vt/vt.c:3516
 process_output_block drivers/tty/n_tty.c:561 [inline]
 n_tty_write+0x7db/0xb10 drivers/tty/n_tty.c:2377
 iterate_tty_write drivers/tty/tty_io.c:1006 [inline]
 file_tty_write+0x38c/0x670 drivers/tty/tty_io.c:1081
 tty_write+0x25/0x30 drivers/tty/tty_io.c:1102
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x49d/0x8e0 fs/read_write.c:686
 ksys_write+0xda/0x1a0 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:746
 x64_sys_call+0x2cdd/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 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: 20044 Comm: syz.4.5395 Not tainted 6.16.0-rc7-syzkaller-00018-g01a412d06bc5 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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