==================================================================
BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff86d2ff08 of 88 bytes by task 31515 on cpu 1:
 prb_reserve+0x6fb/0xaf0 kernel/printk/printk_ringbuffer.c:1693
 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
 set_capacity_and_notify+0x1d5/0x230 block/genhd.c:93
 loop_set_size+0x2e/0x70 drivers/block/loop.c:220
 loop_configure+0x826/0x9c0 drivers/block/loop.c:1075
 lo_ioctl+0x1e1/0x1390 drivers/block/loop.c:1530
 blkdev_ioctl+0x387/0x460 block/ioctl.c:797
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xce/0x140 fs/ioctl.c:583
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583
 x64_sys_call+0x1563/0x3020 arch/x86/include/generated/asm/syscalls_64.h:17
 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 0xffffffff86d2ff08 of 8 bytes by task 31520 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:500 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1934 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1982 [inline]
 _prb_read_valid+0x18c/0x930 kernel/printk/printk_ringbuffer.c:2173
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2245
 __console_flush_and_unlock kernel/printk/printk.c:3392 [inline]
 console_unlock+0x146/0x280 kernel/printk/printk.c:3413
 class_console_lock_destructor include/linux/console.h:734 [inline]
 con_flush_chars drivers/tty/vt/vt.c:3732 [inline]
 con_write+0xca/0x1d0 drivers/tty/vt/vt.c:3662
 process_output_block drivers/tty/n_tty.c:557 [inline]
 n_tty_write+0x7f4/0xb00 drivers/tty/n_tty.c:2366
 iterate_tty_write drivers/tty/tty_io.c:1006 [inline]
 file_tty_write+0x397/0x690 drivers/tty/tty_io.c:1081
 tty_write+0x25/0x30 drivers/tty/tty_io.c:1102
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x57d/0x990 fs/read_write.c:687
 ksys_write+0xdc/0x1a0 fs/read_write.c:739
 __do_sys_write fs/read_write.c:750 [inline]
 __se_sys_write fs/read_write.c:747 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:747
 x64_sys_call+0x27e1/0x3020 arch/x86/include/generated/asm/syscalls_64.h:2
 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

value changed: 0x0000000000003c4d -> 0x0000000000005c4d

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 31520 Comm: syz.7.8370 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================
loop7: detected capacity change from 0 to 512
EXT4-fs (loop7): revision level too high, forcing read-only mode
[EXT4 FS bs=1024, gc=1, bpg=8192, ipg=32, mo=8842c01c, mo2=0002]
EXT4-fs (loop7): orphan cleanup on readonly fs
EXT4-fs error (device loop7): ext4_orphan_get:1399: inode #13: comm syz.7.8370: iget: bad i_size value: 12154761577498
loop7: lost file I/O error report for ino 13 type 5 pos 0x0 len 0x0 error -117
EXT4-fs error (device loop7): ext4_orphan_get:1404: comm syz.7.8370: couldn't read orphan inode 13 (err -117)
loop7: lost filesystem error report for type 5 error -117
EXT4-fs warning (device loop7): dx_probe:861: inode #2: comm syz.7.8370: dx entry: limit 65535 != root limit 120
EXT4-fs warning (device loop7): dx_probe:934: inode #2: comm syz.7.8370: Corrupt directory, running e2fsck is recommended