syzbot

==================================================================
BUG: KCSAN: data-race in data_alloc / data_push_tail

write to 0xffffffff8939d860 of 8 bytes by task 28 on cpu 0:
 data_alloc+0x259/0x390 kernel/printk/printk_ringbuffer.c:1116
 prb_reserve+0x8d7/0xae0 kernel/printk/printk_ringbuffer.c:1724
 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
 kauditd_printk_skb kernel/audit.c:587 [inline]
 kauditd_hold_skb+0x1b1/0x1c0 kernel/audit.c:622
 kauditd_send_queue+0x273/0x2c0 kernel/audit.c:807
 kauditd_thread+0x444/0x670 kernel/audit.c:931
 kthread+0x22a/0x280 kernel/kthread.c:467
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffffffff8939d860 of 8 bytes by task 8974 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: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
 bio_check_eod block/blk-core.c:566 [inline]
 submit_bio_noacct+0x8c7/0x9b0 block/blk-core.c:806
 submit_bio+0x2a4/0x2c0 block/blk-core.c:926
 mpage_bio_submit_write fs/mpage.c:83 [inline]
 mpage_write_folio fs/mpage.c:594 [inline]
 mpage_writepages+0x79d/0x1310 fs/mpage.c:670
 fat_writepages+0x24/0x30 fs/fat/inode.c:200
 do_writepages+0x1c6/0x310 mm/page-writeback.c:2554
 filemap_writeback mm/filemap.c:387 [inline]
 filemap_flush_range+0x105/0x140 mm/filemap.c:436
 generic_fadvise+0x338/0x460 mm/fadvise.c:114
 vfs_fadvise mm/fadvise.c:184 [inline]
 ksys_fadvise64_64 mm/fadvise.c:197 [inline]
 __do_sys_fadvise64 mm/fadvise.c:209 [inline]
 __se_sys_fadvise64 mm/fadvise.c:207 [inline]
 __x64_sys_fadvise64+0xcb/0x110 mm/fadvise.c:207
 x64_sys_call+0x242b/0x3020 arch/x86/include/generated/asm/syscalls_64.h:222
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000fffff143 -> 0x00000000fffffc24

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 8974 Comm: syz.5.1517 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================
syz.5.1517: attempt to access beyond end of device
loop5: rw=1, sector=233, nr_sectors = 8 limit=128
syz.5.1517: attempt to access beyond end of device
loop5: rw=1, sector=249, nr_sectors = 8 limit=128
syz.5.1517: attempt to access beyond end of device
loop5: rw=1, sector=265, nr_sectors = 8 limit=128
syz.5.1517: attempt to access beyond end of device
loop5: rw=1, sector=281, nr_sectors = 8 limit=128
syz.5.1517: attempt to access beyond end of device
loop5: rw=1, sector=297, nr_sectors = 8 limit=128