loop3: detected capacity change from 0 to 1024
EXT4-fs: Ignoring removed nomblk_io_submit option
==================================================================
BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff86c95c78 of 88 bytes by task 28811 on cpu 1:
 prb_reserve+0x6e0/0xad0 kernel/printk/printk_ringbuffer.c:1693
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 __netdev_printk+0x310/0x370 net/core/dev.c:12949
 netdev_info+0xa6/0xd0 net/core/dev.c:12996
 __dev_set_promiscuity+0x1ee/0x3d0 net/core/dev.c:9618
 __dev_change_flags+0x265/0x490 net/core/dev.c:9767
 netif_change_flags+0x5a/0xd0 net/core/dev.c:9821
 dev_change_flags+0xce/0x190 net/core/dev_api.c:68
 dev_ifsioc+0x441/0xfd0 net/core/dev_ioctl.c:555
 dev_ioctl+0x709/0x960 net/core/dev_ioctl.c:816
 sock_do_ioctl+0x1aa/0x230 net/socket.c:1327
 sock_ioctl+0x41b/0x610 net/socket.c:1434
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xce/0x140 fs/ioctl.c:583
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583
 x64_sys_call+0x1563/0x3020 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86c95c78 of 8 bytes by task 28797 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:500 [inline]
 prb_first_seq kernel/printk/printk_ringbuffer.c:2017 [inline]
 _prb_read_valid+0x369/0x950 kernel/printk/printk_ringbuffer.c:2174
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2245
 __console_flush_and_unlock kernel/printk/printk.c:3392 [inline]
 console_unlock+0x146/0x280 kernel/printk/printk.c:3413
 vprintk_emit+0x3e4/0x600 kernel/printk/printk.c:2479
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 __ext4_msg+0x143/0x1c0 fs/ext4/super.c:1003
 ext4_parse_param+0x81d/0xfb0 fs/ext4/super.c:2226
 vfs_parse_fs_param+0x142/0x2a0 fs/fs_context.c:132
 vfs_parse_fs_qstr fs/fs_context.c:173 [inline]
 vfs_parse_fs_string include/linux/fs_context.h:142 [inline]
 vfs_parse_monolithic_sep+0x1e6/0x270 fs/fs_context.c:213
 generic_parse_monolithic+0x24/0x30 fs/fs_context.c:241
 parse_monolithic_mount_data+0x46/0x60 fs/fs_context.c:519
 do_new_mount+0x24e/0x8d0 fs/namespace.c:3830
 path_mount+0x4d0/0xbc0 fs/namespace.c:4154
 do_mount fs/namespace.c:4167 [inline]
 __do_sys_mount fs/namespace.c:4383 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4360
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4360
 x64_sys_call+0x2d61/0x3020 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000002043 -> 0x0000000000004043

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 28797 Comm: syz.3.11111 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================
[EXT4 FS bs=1024, gc=1, bpg=131072, ipg=32, mo=6042c028, mo2=0102]
System zones: 0-1, 3-12
EXT4-fs (loop3): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.