BUG: KCSAN: data-race in data_push_tail / vsnprintf

write to 0xffffffff86e58ea8 of 1 bytes by task 22225 on cpu 1:
 vsnprintf+0xe2a/0xe80
 vscnprintf+0x3e/0x80 lib/vsprintf.c:2889
 printk_sprint kernel/printk/printk.c:2222 [inline]
 vprintk_store+0x5f2/0xb50 kernel/printk/printk.c:2336
 vprintk_emit+0xcc/0x4e0 kernel/printk/printk.c:2382
 vprintk_default+0x22/0x30 kernel/printk/printk.c:2412
 vprintk+0x7f/0x90 kernel/printk/printk_safe.c:50
 _printk+0x76/0x96 kernel/printk/printk.c:2422
 set_capacity_and_notify+0x170/0x1d0 block/genhd.c:90
 loop_set_size+0x2e/0x70 drivers/block/loop.c:237
 loop_configure+0xb52/0xc70 drivers/block/loop.c:1095
 lo_ioctl+0x641/0x1290
 blkdev_ioctl+0x20e/0x440 block/ioctl.c:614
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:856
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

read to 0xffffffff86e58ea8 of 8 bytes by task 22224 on cpu 0:
 data_make_reusable kernel/printk/printk_ringbuffer.c:590 [inline]
 data_push_tail+0x10f/0x440 kernel/printk/printk_ringbuffer.c:675
 data_alloc+0xbc/0x2b0 kernel/printk/printk_ringbuffer.c:1046
 prb_reserve+0x897/0xbd0 kernel/printk/printk_ringbuffer.c:1555
 vprintk_store+0x51c/0xb50 kernel/printk/printk.c:2326
 vprintk_emit+0xcc/0x4e0 kernel/printk/printk.c:2382
 vprintk_default+0x22/0x30 kernel/printk/printk.c:2412
 vprintk+0x7f/0x90 kernel/printk/printk_safe.c:50
 _printk+0x76/0x96 kernel/printk/printk.c:2422
 set_capacity_and_notify+0x170/0x1d0 block/genhd.c:90
 loop_set_size+0x2e/0x70 drivers/block/loop.c:237
 loop_configure+0xb52/0xc70 drivers/block/loop.c:1095
 lo_ioctl+0x641/0x1290
 blkdev_ioctl+0x20e/0x440 block/ioctl.c:614
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:856
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

value changed: 0x0000000100015b43 -> 0x0000000100015b00

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 22224 Comm: syz-executor.3 Not tainted 5.18.0-syzkaller-11793-g8eca6b0a647a-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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isofs_fill_super: root inode is not a directory. Corrupted media?