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

write to 0xffffffff86675d20 of 8 bytes by task 4108 on cpu 1:
 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 0xffffffff86675d20 of 8 bytes by task 4112 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+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
 bpf_get_probe_write_proto+0x8b/0x90 kernel/trace/bpf_trace.c:365
 bpf_tracing_func_proto+0x596/0x790 kernel/trace/bpf_trace.c:1490
 raw_tp_prog_func_proto+0x65/0xc0 kernel/trace/bpf_trace.c:1973
 get_helper_proto kernel/bpf/verifier.c:10641 [inline]
 mark_fastcall_pattern_for_call kernel/bpf/verifier.c:16511 [inline]
 mark_fastcall_patterns+0x566/0xd10 kernel/bpf/verifier.c:16622
 bpf_check+0x3ec1/0xd5e0 kernel/bpf/verifier.c:22661
 bpf_prog_load+0xed4/0x1070 kernel/bpf/syscall.c:2947
 __sys_bpf+0x463/0x7a0 kernel/bpf/syscall.c:5790
 __do_sys_bpf kernel/bpf/syscall.c:5897 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5895 [inline]
 __x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5895
 x64_sys_call+0x2914/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:322
 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: 0x0000000000139c88 -> 0x00000000001dfdc0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 4112 Comm: syz.6.11413 Not tainted 6.13.0-rc7-syzkaller-00019-gc45323b7560e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
==================================================================
syz.6.11413[4112] is installing a program with bpf_probe_write_user helper that may corrupt user memory!
syz.6.11413[4112] is installing a program with bpf_probe_write_user helper that may corrupt user memory!
syz.6.11413[4112] is installing a program with bpf_probe_write_user helper that may corrupt user memory!