loop0: detected capacity change from 0 to 512
==================================================================
BUG: KCSAN: data-race in data_alloc / data_push_tail

write to 0xffffffff86f17ba0 of 8 bytes by task 15147 on cpu 0:
 data_alloc+0x216/0x2c0 kernel/printk/printk_ringbuffer.c:1074
 prb_reserve+0x893/0xbc0 kernel/printk/printk_ringbuffer.c:1555
 vprintk_store+0x536/0x800 kernel/printk/printk.c:2241
 vprintk_emit+0xd0/0x430 kernel/printk/printk.c:2297
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2327
 vprintk+0x83/0x90 kernel/printk/printk_safe.c:50
 _printk+0x7a/0xa0 kernel/printk/printk.c:2337
 __ext4_msg+0x130/0x1a0 fs/ext4/super.c:939
 ext4_parse_param+0x88f/0x1050 fs/ext4/super.c:2119
 vfs_parse_fs_param+0x136/0x290 fs/fs_context.c:146
 vfs_parse_fs_string fs/fs_context.c:184 [inline]
 generic_parse_monolithic+0x165/0x1d0 fs/fs_context.c:224
 parse_monolithic_mount_data+0x42/0x50 fs/fs_context.c:667
 do_new_mount+0x1d3/0x650 fs/namespace.c:3038
 path_mount+0x498/0xb40 fs/namespace.c:3372
 do_mount fs/namespace.c:3385 [inline]
 __do_sys_mount fs/namespace.c:3594 [inline]
 __se_sys_mount+0x27f/0x2d0 fs/namespace.c:3571
 __x64_sys_mount+0x67/0x80 fs/namespace.c:3571
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffffffff86f17ba0 of 8 bytes by task 15149 on cpu 1:
 data_make_reusable kernel/printk/printk_ringbuffer.c:590 [inline]
 data_push_tail+0x102/0x430 kernel/printk/printk_ringbuffer.c:675
 data_alloc+0xbe/0x2c0 kernel/printk/printk_ringbuffer.c:1046
 prb_reserve+0x893/0xbc0 kernel/printk/printk_ringbuffer.c:1555
 vprintk_store+0x536/0x800 kernel/printk/printk.c:2241
 vprintk_emit+0xd0/0x430 kernel/printk/printk.c:2297
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2327
 vprintk+0x83/0x90 kernel/printk/printk_safe.c:50
 _printk+0x7a/0xa0 kernel/printk/printk.c:2337
 set_capacity_and_notify+0x178/0x1d0 block/genhd.c:90
 loop_set_size+0x2e/0x70 drivers/block/loop.c:237
 loop_configure+0xafb/0xc20 drivers/block/loop.c:1100
 lo_ioctl+0x688/0x12f0
 blkdev_ioctl+0x3a0/0x490 block/ioctl.c:615
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xc9/0x140 fs/ioctl.c:856
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00000000ffffe97b -> 0x00000000fffff798

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 15149 Comm: syz-executor.0 Not tainted 6.3.0-rc3-syzkaller-00005-g7d31677bb7b1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
==================================================================
EXT4-fs: Ignoring removed nobh option
EXT4-fs: Ignoring removed mblk_io_submit option
EXT4-fs: Ignoring removed nobh option
EXT4-fs (loop0): 1 truncate cleaned up
EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 without journal. Quota mode: writeback.