==================================================================
BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff86688ff8 of 8 bytes by task 5106 on cpu 0:
 data_alloc+0x291/0x2c0 kernel/printk/printk_ringbuffer.c:1096
 prb_reserve+0x85e/0xb60 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x558/0x870 kernel/printk/printk.c:2326
 vprintk_emit+0x15e/0x680 kernel/printk/printk.c:2408
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2447
 vprintk+0x75/0x80 kernel/printk/printk_safe.c:86
 _printk+0x7a/0xa0 kernel/printk/printk.c:2457
 set_capacity_and_notify+0xff/0x160 block/genhd.c:86
 loop_set_size+0x2e/0x70 drivers/block/loop.c:232
 loop_configure+0x8a6/0xa30 drivers/block/loop.c:1101
 lo_ioctl+0x5f6/0x11c0
 blkdev_ioctl+0x359/0x450 block/ioctl.c:693
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xc9/0x140 fs/ioctl.c:892
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:892
 x64_sys_call+0x1690/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86688ff8 of 8 bytes by task 5105 on cpu 1:
 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+0x235/0xb60 kernel/printk/printk_ringbuffer.c:1619
 vprintk_store+0x558/0x870 kernel/printk/printk.c:2326
 vprintk_emit+0x15e/0x680 kernel/printk/printk.c:2408
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2447
 vprintk+0x75/0x80 kernel/printk/printk_safe.c:86
 _printk+0x7a/0xa0 kernel/printk/printk.c:2457
 __netdev_printk+0x2d1/0x3e0 net/core/dev.c:11946
 netdev_info+0x99/0xc0 net/core/dev.c:11993
 slcan_open+0x24f/0x280 drivers/net/can/slcan/slcan-core.c:850
 tty_ldisc_open+0x65/0xb0 drivers/tty/tty_ldisc.c:432
 tty_set_ldisc+0x205/0x3b0 drivers/tty/tty_ldisc.c:563
 tiocsetd+0x52/0x60 drivers/tty/tty_io.c:2439
 tty_ioctl+0xa94/0xbe0 drivers/tty/tty_io.c:2739
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xc9/0x140 fs/ioctl.c:892
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:892
 x64_sys_call+0x1690/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000189870 -> 0x0000000000239488

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 5105 Comm: syz.8.11674 Not tainted 6.13.0-rc4-syzkaller-00071-gfd0584d220fe #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
==================================================================
can0: slcan on ttyS3.
can0 (unregistered): slcan off ttyS3.