FAT-fs (loop3): Can't find a valid FAT filesystem
loop3: detected capacity change from 0 to 264192
------------[ cut here ]------------
percpu ref (css_release) <= 0 (-1) after switching to atomic
WARNING: lib/percpu-refcount.c:197 at percpu_ref_switch_to_atomic_rcu+0x3cc/0x480, CPU#0: syz-executor/8366
Modules linked in:
CPU: 0 UID: 0 PID: 8366 Comm: syz-executor Tainted: G        W           6.17.0-rc4-next-20250901 #1 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
RIP: 0010:percpu_ref_switch_to_atomic_rcu+0x3cc/0x480
Code: 00 00 00 00 00 fc ff df 48 89 f9 48 c1 e9 03 80 3c 01 00 0f 85 9e 00 00 00 49 8b 75 e8 48 c7 c7 c0 99 e2 84 e8 25 ac e9 fe 90 <0f> 0b 90 90 e9 2b ff ff ff e8 56 de 5f ff e9 9e fe ff ff e8 dc de
RSP: 0018:ffff88806ce08e20 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff8139de70
RDX: ffff8880177ad280 RSI: ffffffff8139de7e RDI: 0000000000000001
RBP: 7fffffffffffffff R08: 0000000000000001 R09: ffffed100d9c4801
R10: 0000000000000000 R11: 0000000000000001 R12: ffff88800d32dd80
R13: ffff88800d32dda0 R14: 0000000000000002 R15: 0000000000000003
FS:  0000555559ff8400(0000) GS:ffff8880e55d8000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fffe7acf000 CR3: 000000000d6e2000 CR4: 0000000000350ef0
Call Trace:
 <IRQ>
 rcu_core+0x7c8/0x1800
 handle_softirqs+0x1b1/0x770
 __irq_exit_rcu+0xc4/0x100
 irq_exit_rcu+0x9/0x20
 sysvec_apic_timer_interrupt+0x70/0x80
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20
RIP: 0010:lock_release+0x152/0x290
Code: 84 e0 00 00 00 b8 ff ff ff ff 65 0f c1 05 ce e5 32 06 83 f8 01 0f 85 f6 00 00 00 41 f7 c5 00 02 00 00 74 01 fb 48 8b 44 24 10 <65> 48 2b 05 ee a5 32 06 0f 85 27 01 00 00 48 83 c4 18 5d 41 5c 41
RSP: 0018:ffff88803ce7fc00 EFLAGS: 00000206
RAX: c50b2d2caa080500 RBX: 000000000000c2d6 RCX: ffff88803ce7fc0c
RDX: 0000000000000002 RSI: ffffffff85c1c6a0 RDI: ffff8880177add28
RBP: ffffffff85c1c6a0 R08: 0000000000000001 R09: ffffffff81b37338
R10: 0000000000000001 R11: 0000000000000001 R12: ffffffff81b373c4
R13: 0000000000000202 R14: ffff8880177ad280 R15: 0000000000000003
 kmemleak_scan+0x3b9/0xe00
 kmemleak_write+0x410/0x4f0
 full_proxy_write+0x133/0x1a0
 vfs_write+0x2b7/0x1150
 ksys_write+0x121/0x240
 do_syscall_64+0xbf/0x360
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4bccba05c3
Code: 16 00 00 00 eb ae 90 b8 6e 00 00 00 eb a6 e8 44 ef 04 00 0f 1f 40 00 64 8b 04 25 18 00 00 00 85 c0 75 14 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 55 c3 0f 1f 40 00 48 83 ec 28 48 89 54 24 18
RSP: 002b:00007ffdfef247b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007ffdfef24df8 RCX: 00007f4bccba05c3
RDX: 0000000000000004 RSI: 00007f4bccc56ed9 RDI: 0000000000000003
RBP: 0000000000000003 R08: 00264abbefdd1c28 R09: 00007f4bcccdd000
R10: 00007f4bcccdd010 R11: 0000000000000246 R12: 00007f4bccba2b10
R13: 00007ffdfef26ee7 R14: 0000000000000000 R15: 00000000000dc20b
 </TASK>
irq event stamp: 644642
hardirqs last  enabled at (644652): [<ffffffff81541b18>] __up_console_sem+0x78/0x80
hardirqs last disabled at (644659): [<ffffffff81541afd>] __up_console_sem+0x5d/0x80
softirqs last  enabled at (643814): [<ffffffff813bafcc>] handle_softirqs+0x50c/0x770
softirqs last disabled at (644011): [<ffffffff813bb364>] __irq_exit_rcu+0xc4/0x100
---[ end trace 0000000000000000 ]---
percpu_ref_switch_to_atomic_rcu: percpu_ref_switch_to_atomic_rcu(): percpu_ref underflow slab kmalloc-64 start ffff88800d32dd80 pointer offset 0 size 64
percpu_ref_switch_to_atomic_rcu: percpu_ref_switch_to_atomic_rcu(): percpu_ref underflow slab kmalloc-64 start ffff88803d3af180 pointer offset 0 size 64
loop4: detected capacity change from 0 to 10
vfat: Unknown parameter 'uid<00000000000000060928'
FAT-fs (loop3): invalid media value (0x2f)
FAT-fs (loop3): Can't find a valid FAT filesystem
loop6: detected capacity change from 0 to 22
loop3: detected capacity change from 0 to 264192
I/O error, dev loop2, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
FAT-fs (loop2): unable to read boot sector
kmemleak: Found object by alias at 0x607f1a63d18c
CPU: 1 UID: 0 PID: 8373 Comm: syz-executor.3 Tainted: G        W           6.17.0-rc4-next-20250901 #1 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xca/0x120
 __lookup_object+0x94/0xb0
 delete_object_full+0x27/0x70
 free_percpu+0x30/0x1160
 futex_hash_free+0x38/0xc0
 mmput+0x2d3/0x390
 do_exit+0x79d/0x2970
 do_group_exit+0xd3/0x2a0
 __x64_sys_exit_group+0x3e/0x50
 x64_sys_call+0x18c5/0x18d0
 do_syscall_64+0xbf/0x360
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5b75b7eb19
Code: Unable to access opcode bytes at 0x7f5b75b7eaef.
RSP: 002b:00007ffdcfddf2f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 000000000000001e RCX: 00007f5b75b7eb19
RDX: 00007f5b75b3172b RSI: ffffffffffffffbc RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000001b2ce27884 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 0000000000000000 R14: 0000000000000001 R15: 00007ffdcfddf3e0
 </TASK>
kmemleak: Object (percpu) 0x607f1a63d188 (size 8):
kmemleak:   comm "syz-executor.6", pid 8387, jiffies 4295577836
kmemleak:   min_count = 1
kmemleak:   count = 0
kmemleak:   flags = 0x21
kmemleak:   checksum = 0
kmemleak:   backtrace:
 pcpu_alloc_noprof+0x87a/0x1170
 alloc_vfsmnt+0x135/0x6e0
 clone_mnt+0x6c/0xb70
 __do_loopback+0x438/0x520
 path_mount+0x19b4/0x1dd0
 __x64_sys_mount+0x27b/0x300
 do_syscall_64+0xbf/0x360
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
loop2: detected capacity change from 0 to 264192
loop6: detected capacity change from 0 to 264192
vfat: Unknown parameter 'uid<00000000000000060928'
vfat: Unknown parameter 'uid<00000000000000060928'
FAT-fs (loop3): invalid media value (0x2f)
FAT-fs (loop3): Can't find a valid FAT filesystem
loop3: detected capacity change from 0 to 264192
----------------
Code disassembly (best guess):
   0:	84 e0                	test   %ah,%al
   2:	00 00                	add    %al,(%rax)
   4:	00 b8 ff ff ff ff    	add    %bh,-0x1(%rax)
   a:	65 0f c1 05 ce e5 32 	xadd   %eax,%gs:0x632e5ce(%rip)        # 0x632e5e0
  11:	06
  12:	83 f8 01             	cmp    $0x1,%eax
  15:	0f 85 f6 00 00 00    	jne    0x111
  1b:	41 f7 c5 00 02 00 00 	test   $0x200,%r13d
  22:	74 01                	je     0x25
  24:	fb                   	sti
  25:	48 8b 44 24 10       	mov    0x10(%rsp),%rax
* 2a:	65 48 2b 05 ee a5 32 	sub    %gs:0x632a5ee(%rip),%rax        # 0x632a620 <-- trapping instruction
  31:	06
  32:	0f 85 27 01 00 00    	jne    0x15f
  38:	48 83 c4 18          	add    $0x18,%rsp
  3c:	5d                   	pop    %rbp
  3d:	41 5c                	pop    %r12
  3f:	41                   	rex.B