audit: type=1326 audit(1752734453.358:24267): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=root:sysadm_r:sysadm_t pid=28773 comm="syz.4.7152" exe="/root/syz-executor" sig=0 arch=c000003e syscall=202 compat=0 ip=0x7f01ae26e929 code=0x7ffc0000
audit: type=1326 audit(1752734453.358:24268): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=root:sysadm_r:sysadm_t pid=28773 comm="syz.4.7152" exe="/root/syz-executor" sig=0 arch=c000003e syscall=202 compat=0 ip=0x7f01ae26e929 code=0x7ffc0000
audit: type=1326 audit(1752734453.358:24269): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=root:sysadm_r:sysadm_t pid=28773 comm="syz.4.7152" exe="/root/syz-executor" sig=0 arch=c000003e syscall=206 compat=0 ip=0x7f01ae26e929 code=0x7ffc0000
==================================================================
BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff8688ae38 of 8 bytes by task 28778 on cpu 1:
 data_alloc+0x27d/0x2b0 kernel/printk/printk_ringbuffer.c:1096
 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
 set_capacity_and_notify+0x14c/0x1f0 block/genhd.c:93
 loop_set_size+0x2e/0x70 drivers/block/loop.c:210
 loop_configure+0x8d3/0xa50 drivers/block/loop.c:1068
 lo_ioctl+0x559/0x15d0 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:907 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:893
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:893
 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+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff8688ae38 of 8 bytes by task 29 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:482 [inline]
 desc_push_tail kernel/printk/printk_ringbuffer.c:778 [inline]
 desc_reserve kernel/printk/printk_ringbuffer.c:924 [inline]
 prb_reserve+0x221/0xaf0 kernel/printk/printk_ringbuffer.c:1619
 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
 kauditd_printk_skb kernel/audit.c:546 [inline]
 kauditd_hold_skb+0x1b1/0x1c0 kernel/audit.c:581
 kauditd_send_queue+0x273/0x2c0 kernel/audit.c:766
 kauditd_thread+0x421/0x630 kernel/audit.c:890
 kthread+0x489/0x510 kernel/kthread.c:464
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x00000000000dcbd0 -> 0x000000000018cd28

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 29 Comm: kauditd Not tainted 6.16.0-rc6-syzkaller-00037-ge2291551827f #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================
audit: type=1326 audit(1752734453.358:24270): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=root:sysadm_r:sysadm_t pid=28773 comm="syz.4.7152" exe="/root/syz-executor" sig=0 arch=c000003e syscall=202 compat=0 ip=0x7f01ae26e929 code=0x7ffc0000
audit: type=1326 audit(1752734453.368:24271): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=root:sysadm_r:sysadm_t pid=28763 comm="syz.9.7149" exe="/root/syz-executor" sig=0 arch=c000003e syscall=202 compat=0 ip=0x7fd0efc4e929 code=0x7ffc0000
audit: type=1326 audit(1752734453.368:24272): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=root:sysadm_r:sysadm_t pid=28763 comm="syz.9.7149" exe="/root/syz-executor" sig=0 arch=c000003e syscall=202 compat=0 ip=0x7fd0efc4e929 code=0x7ffc0000
audit: type=1326 audit(1752734453.368:24273): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=root:sysadm_r:sysadm_t pid=28763 comm="syz.9.7149" exe="/root/syz-executor" sig=0 arch=c000003e syscall=321 compat=0 ip=0x7fd0efc4e929 code=0x7ffc0000
audit: type=1326 audit(1752734453.368:24274): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=root:sysadm_r:sysadm_t pid=28763 comm="syz.9.7149" exe="/root/syz-executor" sig=0 arch=c000003e syscall=202 compat=0 ip=0x7fd0efc4e929 code=0x7ffc0000
audit: type=1326 audit(1752734453.368:24275): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=root:sysadm_r:sysadm_t pid=28763 comm="syz.9.7149" exe="/root/syz-executor" sig=0 arch=c000003e syscall=28 compat=0 ip=0x7fd0efc4e929 code=0x7ffc0000
audit: type=1326 audit(1752734453.368:24276): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=root:sysadm_r:sysadm_t pid=28763 comm="syz.9.7149" exe="/root/syz-executor" sig=0 arch=c000003e syscall=202 compat=0 ip=0x7fd0efc4e929 code=0x7ffc0000