syzbot

ext4 filesystem being mounted at /156/file0 supports timestamps until 2038-01-19 (0x7fffffff)
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BUG: KCSAN: data-race in data_push_tail / vsnprintf

write to 0xffffffff89117fc2 of 9 bytes by task 1681 on cpu 0:
 vsnprintf+0x2ce/0x860 lib/vsprintf.c:2898
 vscnprintf+0x41/0x90 lib/vsprintf.c:3012
 printk_sprint+0x30/0x2c0 kernel/printk/printk.c:2192
 vprintk_store+0x57b/0x910 kernel/printk/printk.c:2312
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2402
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2441
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2451
 __ext4_msg+0x1aa/0x1c0 fs/ext4/super.c:990
 ext4_quota_write+0x108/0x360 fs/ext4/super.c:-1
 v2_write_file_info+0x1b6/0x250 fs/quota/quota_v2.c:218
 dquot_release+0x1af/0x210 fs/quota/dquot.c:543
 ext4_release_dquot+0x1e3/0x460 fs/ext4/super.c:-1
 quota_release_workfn+0x260/0x540 fs/quota/dquot.c:843
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0x4cd/0x9d0 kernel/workqueue.c:3340
 worker_thread+0x6bc/0x8b0 kernel/workqueue.c:3421
 kthread+0x488/0x510 kernel/kthread.c:463
 ret_from_fork+0x148/0x280 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

read to 0xffffffff89117fc8 of 8 bytes by task 19009 on cpu 1:
 data_make_reusable kernel/printk/printk_ringbuffer.c:608 [inline]
 data_push_tail+0x100/0x470 kernel/printk/printk_ringbuffer.c:693
 data_alloc+0x11b/0x390 kernel/printk/printk_ringbuffer.c:1089
 prb_reserve+0x8d7/0xae0 kernel/printk/printk_ringbuffer.c:1724
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2302
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2402
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2441
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2451
 mnt_warn_timestamp_expiry+0x1c3/0x200 fs/namespace.c:3178
 do_new_mount_fc fs/namespace.c:3652 [inline]
 do_new_mount+0x356/0x700 fs/namespace.c:3712
 path_mount+0x4d0/0xbc0 fs/namespace.c:4022
 do_mount fs/namespace.c:4035 [inline]
 __do_sys_mount fs/namespace.c:4224 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4201
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4201
 x64_sys_call+0x2cca/0x3000 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000ffffeeeb -> 0x3a2932706f6f6c28

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 19009 Comm: syz.2.4978 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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