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

write to 0xffffffff870ef718 of 1 bytes by task 30916 on cpu 1:
 string_nocheck lib/vsprintf.c:650 [inline]
 string+0x16c/0x200 lib/vsprintf.c:728
 vsnprintf+0xa09/0xe30 lib/vsprintf.c:2824
 vscnprintf+0x42/0x80 lib/vsprintf.c:2930
 printk_sprint+0x30/0x2d0 kernel/printk/printk.c:2124
 vprintk_store+0x56f/0x800 kernel/printk/printk.c:2238
 vprintk_emit+0xd0/0x5d0 kernel/printk/printk.c:2284
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2318
 vprintk+0x71/0x80 kernel/printk/printk_safe.c:45
 _printk+0x7a/0xa0 kernel/printk/printk.c:2328
 dump_stack_print_info+0x11d/0x120 lib/dump_stack.c:66
 __dump_stack lib/dump_stack.c:87 [inline]
 dump_stack_lvl+0xce/0x130 lib/dump_stack.c:106
 dump_stack+0x15/0x20 lib/dump_stack.c:113
 fail_dump lib/fault-inject.c:52 [inline]
 should_fail_ex+0x21f/0x230 lib/fault-inject.c:153
 __should_fail_alloc_page+0xfd/0x110 mm/fail_page_alloc.c:42
 prepare_alloc_pages mm/page_alloc.c:4340 [inline]
 __alloc_pages+0x108/0x340 mm/page_alloc.c:4556
 alloc_pages_mpol+0xb1/0x1d0 mm/mempolicy.c:2133
 vma_alloc_folio+0x166/0x2b0 mm/mempolicy.c:2172
 wp_page_copy mm/memory.c:3138 [inline]
 do_wp_page+0x61b/0x1f20 mm/memory.c:3525
 handle_pte_fault mm/memory.c:5160 [inline]
 __handle_mm_fault mm/memory.c:5285 [inline]
 handle_mm_fault+0xb80/0x27c0 mm/memory.c:5450
 do_user_addr_fault arch/x86/mm/fault.c:1415 [inline]
 handle_page_fault arch/x86/mm/fault.c:1507 [inline]
 exc_page_fault+0x2f9/0x6d0 arch/x86/mm/fault.c:1563
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570

read to 0xffffffff870ef718 of 8 bytes by task 30919 on cpu 0:
 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+0x897/0xbc0 kernel/printk/printk_ringbuffer.c:1555
 vprintk_store+0x53e/0x800 kernel/printk/printk.c:2228
 vprintk_emit+0xd0/0x5d0 kernel/printk/printk.c:2284
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2318
 vprintk+0x71/0x80 kernel/printk/printk_safe.c:45
 _printk+0x7a/0xa0 kernel/printk/printk.c:2328
 set_capacity_and_notify+0x11d/0x170 block/genhd.c:86
 loop_set_size+0x2e/0x70 drivers/block/loop.c:235
 loop_configure+0xaf9/0xca0 drivers/block/loop.c:1096
 lo_ioctl+0x682/0x12e0
 blkdev_ioctl+0x375/0x460 block/ioctl.c:634
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xcf/0x140 fs/ioctl.c:857
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00000001000065a2 -> 0x676e452065747570

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 30919 Comm: syz-executor.0 Not tainted 6.8.0-rc4-syzkaller-00005-gc664e16bb1ba #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
==================================================================
EXT4-fs: Ignoring removed oldalloc option
EXT4-fs: Ignoring removed bh option
EXT4-fs: Quota format mount options ignored when QUOTA feature is enabled
EXT4-fs (loop0): 1 orphan inode deleted
EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback.
ext4 filesystem being mounted at /root/syzkaller-testdir1136096007/syzkaller.qmM9Zj/2009/file1 supports timestamps until 2038-01-19 (0x7fffffff)