loop4: detected capacity change from 0 to 1024
==================================================================
BUG: KCSAN: data-race in data_push_tail / vsnprintf

write to 0xffffffff88bd08e5 of 1 bytes by task 7575 on cpu 0:
 vsnprintf+0x844/0x890
 vscnprintf+0x42/0x90 lib/vsprintf.c:2908
 printk_sprint+0x30/0x2d0 kernel/printk/printk.c:2216
 vprintk_store+0x589/0x870 kernel/printk/printk.c:2336
 vprintk_emit+0x15e/0x680 kernel/printk/printk.c:2408
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2447
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x7a/0xa0 kernel/printk/printk.c:2457
 blk_add_partition block/partitions/core.c:540 [inline]
 blk_add_partitions block/partitions/core.c:633 [inline]
 bdev_disk_changed+0x833/0xb90 block/partitions/core.c:693
 loop_reread_partitions drivers/block/loop.c:537 [inline]
 loop_set_status+0x4a9/0x540 drivers/block/loop.c:1304
 lo_ioctl+0x807/0x1400
 blkdev_ioctl+0x359/0x450 block/ioctl.c:693
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xc9/0x140 fs/ioctl.c:892
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:892
 x64_sys_call+0x1690/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff88bd08e0 of 8 bytes by task 7598 on cpu 1:
 data_make_reusable kernel/printk/printk_ringbuffer.c:594 [inline]
 data_push_tail+0x102/0x430 kernel/printk/printk_ringbuffer.c:679
 data_alloc+0xbe/0x2c0 kernel/printk/printk_ringbuffer.c:1054
 prb_reserve+0x85e/0xb60 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x558/0x870 kernel/printk/printk.c:2326
 vprintk_emit+0x15e/0x680 kernel/printk/printk.c:2408
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2447
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x7a/0xa0 kernel/printk/printk.c:2457
 set_capacity_and_notify+0x151/0x200 block/genhd.c:93
 loop_set_size+0x2e/0x70 drivers/block/loop.c:234
 loop_configure+0x8bd/0xa50 drivers/block/loop.c:1105
 lo_ioctl+0x607/0x1400
 blkdev_ioctl+0x359/0x450 block/ioctl.c:693
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xc9/0x140 fs/ioctl.c:892
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:892
 x64_sys_call+0x1690/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000100003b5f -> 0x000000202c444f45

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 7598 Comm: syz.4.11034 Not tainted 6.13.0-syzkaller-07644-gc2da8b3f914f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
==================================================================
EXT4-fs (loop4): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback.
EXT4-fs (loop4): unmounting filesystem 00000000-0000-0000-0000-000000000000.