syzbot

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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve_in_last

write to 0xffffffff86c8f250 of 8 bytes by interrupt on cpu 1:
 data_realloc kernel/printk/printk_ringbuffer.c:1228 [inline]
 prb_reserve_in_last+0x9c7/0xae0 kernel/printk/printk_ringbuffer.c:1498
 vprintk_store+0x457/0x910 kernel/printk/printk.c:2328
 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+0x2c7/0x300 fs/ext4/super.c:3710
 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+0x40c/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:1062 [inline]
 sysvec_apic_timer_interrupt+0x74/0x80 arch/x86/kernel/apic/apic.c:1062
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
 console_flush_one_record arch/x86/include/asm/irqflags.h:-1 [inline]
 console_flush_all+0x513/0x6b0 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
 __ext4_msg+0x1aa/0x1c0 fs/ext4/super.c:1001
 ext4_handle_error+0x527/0x570 fs/ext4/super.c:741
 __ext4_error_inode+0x1af/0x3a0 fs/ext4/super.c:871
 __check_block_validity fs/ext4/inode.c:403 [inline]
 ext4_map_blocks+0x6cf/0x950 fs/ext4/inode.c:-1
 ext4_getblk+0x135/0x540 fs/ext4/inode.c:992
 ext4_bread+0x28/0x110 fs/ext4/inode.c:1055
 ext4_quota_write+0x166/0x360 fs/ext4/super.c:7405
 write_blk+0x8a/0x100 fs/quota/quota_tree.c:70
 do_insert_tree+0x954/0xad0 fs/quota/quota_tree.c:407
 dq_insert_tree fs/quota/quota_tree.c:432 [inline]
 qtree_write_dquot+0x2b7/0x2e0 fs/quota/quota_tree.c:451
 v2_write_dquot+0xcb/0x130 fs/quota/quota_v2.c:372
 dquot_acquire+0x1bc/0x2b0 fs/quota/dquot.c:498
 ext4_acquire_dquot+0x15f/0x200 fs/ext4/super.c:7037
 dqget+0x51f/0x8b0 fs/quota/dquot.c:1002
 __dquot_initialize+0x28c/0x7c0 fs/quota/dquot.c:1530
 dquot_initialize+0x1a/0x30 fs/quota/dquot.c:1592
 ext4_process_orphan+0x2d/0x1c0 fs/ext4/orphan.c:327
 ext4_orphan_cleanup+0x6a6/0xa10 fs/ext4/orphan.c:472
 __ext4_fill_super fs/ext4/super.c:5705 [inline]
 ext4_fill_super+0x33ab/0x3760 fs/ext4/super.c:5828
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1634
 get_tree_bdev+0x1f/0x30 fs/super.c:1657
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5860
 vfs_get_tree+0x57/0x1d0 fs/super.c:1694
 fc_mount fs/namespace.c:1198 [inline]
 do_new_mount_fc fs/namespace.c:3765 [inline]
 do_new_mount+0x288/0x8d0 fs/namespace.c:3841
 path_mount+0x4ad/0xb90 fs/namespace.c:4161
 do_mount fs/namespace.c:4174 [inline]
 __do_sys_mount fs/namespace.c:4390 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4367
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4367
 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+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86c8f248 of 16 bytes by task 2968 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+0x258/0x560 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+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+0x136/0x3c0 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: 2968 Comm: klogd Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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