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BUG: KCSAN: data-race in data_push_tail / vsnprintf

write to 0xffffffff88e1dbf0 of 43 bytes by task 16735 on cpu 0:
 vsnprintf+0x2ce/0x890 lib/vsprintf.c:2804
 vscnprintf+0x41/0x90 lib/vsprintf.c:2917
 printk_sprint+0x30/0x2d0 kernel/printk/printk.c:2216
 vprintk_store+0x599/0x860 kernel/printk/printk.c:2336
 vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2475
 fail_dump lib/fault-inject.c:66 [inline]
 should_fail_ex+0x24d/0x280 lib/fault-inject.c:174
 should_failslab+0x8c/0xb0 mm/failslab.c:46
 slab_pre_alloc_hook mm/slub.c:4114 [inline]
 slab_alloc_node mm/slub.c:4190 [inline]
 __do_kmalloc_node mm/slub.c:4340 [inline]
 __kvmalloc_node_noprof+0x126/0x4d0 mm/slub.c:5026
 vmemdup_user+0x26/0xd0 mm/util.c:246
 setxattr_copy fs/xattr.c:619 [inline]
 path_setxattrat+0x1b6/0x310 fs/xattr.c:701
 __do_sys_lsetxattr fs/xattr.c:754 [inline]
 __se_sys_lsetxattr fs/xattr.c:750 [inline]
 __x64_sys_lsetxattr+0x71/0x90 fs/xattr.c:750
 x64_sys_call+0x1e36/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:190
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff88e1dc00 of 8 bytes by task 16728 on cpu 1:
 data_make_reusable kernel/printk/printk_ringbuffer.c:594 [inline]
 data_push_tail+0xfd/0x420 kernel/printk/printk_ringbuffer.c:679
 data_alloc+0xbf/0x2b0 kernel/printk/printk_ringbuffer.c:1054
 prb_reserve+0x808/0xaf0 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2475
 check_partition block/partitions/core.c:153 [inline]
 blk_add_partitions block/partitions/core.c:589 [inline]
 bdev_disk_changed+0x9f1/0xcb0 block/partitions/core.c:693
 loop_reread_partitions drivers/block/loop.c:436 [inline]
 loop_set_status+0x516/0x5c0 drivers/block/loop.c:1243
 lo_ioctl+0x7fa/0x1560 drivers/block/loop.c:-1
 blkdev_ioctl+0x34f/0x440 block/ioctl.c:704
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:892
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:892
 x64_sys_call+0x19a8/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000ffffffd4 -> 0x676e6963726f6620

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 16728 Comm: syz.5.4126 Not tainted 6.15.0-rc3-syzkaller-00283-gf1a3944c860b #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
==================================================================
loop5: p4 size 8388608 extends beyond EOD, truncated