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BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff86c76eb0 of 8 bytes by interrupt on cpu 1:
 data_alloc+0x310/0x390 kernel/printk/printk_ringbuffer.c:1129
 prb_reserve+0x8d6/0xad0 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
 print_daily_error_info+0x210/0x300 fs/ext4/super.c:3712
 call_timer_fn+0x3b/0x240 kernel/time/timer.c:1748
 expire_timers kernel/time/timer.c:1799 [inline]
 __run_timers kernel/time/timer.c:2374 [inline]
 __run_timer_base+0x415/0x5f0 kernel/time/timer.c:2386
 run_timer_base kernel/time/timer.c:2395 [inline]
 run_timer_softirq+0x31/0x70 kernel/time/timer.c:2405
 handle_softirqs+0xb9/0x280 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0x42/0xd0 kernel/softirq.c:735
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
 sysvec_apic_timer_interrupt+0x74/0x80 arch/x86/kernel/apic/apic.c:1061
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
 __tsan_read1+0x12/0x180 kernel/kcsan/core.c:1022
 printk_percpu_data_ready+0x15/0x30 kernel/printk/printk.c:535
 nbcon_get_cpu_emergency_nesting+0xa/0x40 kernel/printk/nbcon.c:1424
 nbcon_get_default_prio+0x2e/0x60 kernel/printk/nbcon.c:1449
 printk_get_console_flush_type+0x1d/0x350 kernel/printk/internal.h:198
 vprintk_emit+0x9f/0x600 kernel/printk/printk.c:2444
 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
 __ext4_error_inode+0x2af/0x3c0 fs/ext4/super.c:861
 __ext4_mark_inode_dirty+0xbd/0x3d0 fs/ext4/inode.c:6561
 ext4_dirty_inode+0x92/0xc0 fs/ext4/inode.c:6587
 __mark_inode_dirty+0x16f/0x710 fs/fs-writeback.c:2623
 mark_inode_dirty_sync include/linux/fs.h:2218 [inline]
 dquot_free_space include/linux/quotaops.h:373 [inline]
 dquot_free_block include/linux/quotaops.h:383 [inline]
 ext4_mb_clear_bb fs/ext4/mballoc.c:6662 [inline]
 ext4_free_blocks+0xea9/0x1430 fs/ext4/mballoc.c:6782
 ext4_remove_blocks fs/ext4/extents.c:2569 [inline]
 ext4_ext_rm_leaf fs/ext4/extents.c:2734 [inline]
 ext4_ext_remove_space+0x1875/0x2950 fs/ext4/extents.c:2979
 ext4_ext_truncate+0xc7/0x160 fs/ext4/extents.c:4566
 ext4_truncate+0x6ea/0xa10 fs/ext4/inode.c:4667
 ext4_process_orphan+0x110/0x1c0 fs/ext4/orphan.c:337
 ext4_orphan_cleanup+0x69c/0x9f0 fs/ext4/orphan.c:472
 __ext4_fill_super fs/ext4/super.c:5701 [inline]
 ext4_fill_super+0x3408/0x37c0 fs/ext4/super.c:5824
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1694
 get_tree_bdev+0x1f/0x30 fs/super.c:1717
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5856
 vfs_get_tree+0x57/0x1d0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3758 [inline]
 do_new_mount+0x288/0x8d0 fs/namespace.c:3834
 path_mount+0x4d0/0xbc0 fs/namespace.c:4154
 do_mount fs/namespace.c:4167 [inline]
 __do_sys_mount fs/namespace.c:4383 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4360
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4360
 x64_sys_call+0x2d61/0x3020 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86c76eb0 of 16 bytes by task 2970 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+0x1b6/0x950 kernel/printk/printk_ringbuffer.c:2173
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2245
 syslog_print+0x109/0x560 kernel/printk/printk.c:1611
 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+0x2b9e/0x3020 arch/x86/include/generated/asm/syscalls_64.h:104
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 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: 2970 Comm: klogd Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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