9p: Bad value for 'rfdno'
==================================================================
BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff86ccaff8 of 88 bytes by task 28 on cpu 1:
 prb_reserve+0x6e6/0xae0 kernel/printk/printk_ringbuffer.c:1690
 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
 kauditd_printk_skb kernel/audit.c:587 [inline]
 kauditd_hold_skb+0x1b1/0x1c0 kernel/audit.c:622
 kauditd_send_queue+0x273/0x2c0 kernel/audit.c:807
 kauditd_thread+0x444/0x670 kernel/audit.c:931
 kthread+0x22a/0x280 kernel/kthread.c:436
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffffffff86ccaff8 of 8 bytes by task 21711 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:500 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1931 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1979 [inline]
 _prb_read_valid+0x1c4/0x950 kernel/printk/printk_ringbuffer.c:2170
 desc_update_last_finalized+0x8f/0x170 kernel/printk/printk_ringbuffer.c:1570
 prb_final_commit+0x10d/0x150 kernel/printk/printk_ringbuffer.c:1839
 vprintk_store+0x88b/0x910 kernel/printk/printk.c:2381
 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
 logfc+0x2d5/0x2e0 fs/fs_context.c:-1
 fs_param_bad_value fs/fs_parser.c:196 [inline]
 fs_param_is_u32+0x121/0x150 fs/fs_parser.c:-1
 __fs_parse+0x29a/0x420 fs/fs_parser.c:129
 fs_parse include/linux/fs_parser.h:76 [inline]
 v9fs_parse_param+0x63/0x980 fs/9p/v9fs.c:223
 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:520
 do_new_mount+0x24e/0x8d0 fs/namespace.c:3835
 path_mount+0x4d0/0xbc0 fs/namespace.c:4159
 do_mount fs/namespace.c:4172 [inline]
 __do_sys_mount fs/namespace.c:4361 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4338
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4338
 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/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000000000293d -> 0x000000000000493d

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 21711 Comm: syz.5.21375 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================
loop5: detected capacity change from 0 to 512
EXT4-fs (loop5): feature flags set on rev 0 fs, running e2fsck is recommended
EXT4-fs (loop5): mounting ext2 file system using the ext4 subsystem
[EXT4 FS bs=2048, gc=1, bpg=16384, ipg=32, mo=a002e01c, mo2=0006]
System zones: 0-2, 18-18, 34-35
EXT4-fs (loop5): mounted filesystem 00000000-0000-0000-0000-000000000000 ro without journal. Quota mode: none.
EXT4-fs (loop5): unmounting filesystem 00000000-0000-0000-0000-000000000000.