------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 0 PID: 7916 at lib/refcount.c:25 refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:25
Modules linked in:
CPU: 0 UID: 0 PID: 7916 Comm: syz.2.533 Not tainted 6.15.0-next-20250528-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:25
Code: 00 00 e8 a9 c0 ff fc 5b 41 5e e9 91 92 a7 06 cc e8 9b c0 ff fc c6 05 b4 a7 ca 0a 01 90 48 c7 c7 00 4c e2 8b e8 37 6e c3 fc 90 <0f> 0b 90 90 eb d7 e8 7b c0 ff fc c6 05 95 a7 ca 0a 01 90 48 c7 c7
RSP: 0018:ffffc90000007828 EFLAGS: 00010246
RAX: e58b95705d451700 RBX: 0000000000000002 RCX: ffff88807b530000
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000002
RBP: ffffc900000079b0 R08: ffffffff8fa132f7 R09: 1ffffffff1f4265e
R10: dffffc0000000000 R11: fffffbfff1f4265f R12: ffff888034022080
R13: dffffc0000000000 R14: ffff8880340221ec R15: ffff8880323b0c00
FS:  00007f6aeb88f6c0(0000) GS:ffff888125c55000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c32aeab CR3: 0000000033eda000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 __refcount_add include/linux/refcount.h:-1 [inline]
 __refcount_inc include/linux/refcount.h:366 [inline]
 refcount_inc include/linux/refcount.h:383 [inline]
 get_net include/net/net_namespace.h:268 [inline]
 tipc_aead_encrypt net/tipc/crypto.c:821 [inline]
 tipc_crypto_xmit+0x1820/0x22c0 net/tipc/crypto.c:1761
 tipc_bearer_xmit_skb+0x245/0x400 net/tipc/bearer.c:572
 tipc_disc_timeout+0x580/0x6d0 net/tipc/discover.c:338
 call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1747
 expire_timers kernel/time/timer.c:1798 [inline]
 __run_timers kernel/time/timer.c:2372 [inline]
 __run_timer_base+0x61a/0x860 kernel/time/timer.c:2384
 run_timer_base kernel/time/timer.c:2393 [inline]
 run_timer_softirq+0xb7/0x180 kernel/time/timer.c:2403
 handle_softirqs+0x283/0x870 kernel/softirq.c:579
 __do_softirq kernel/softirq.c:613 [inline]
 invoke_softirq kernel/softirq.c:453 [inline]
 __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:696
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1050
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:shmem_add_to_page_cache+0x8a7/0xb10 mm/shmem.c:919
Code: 8b a4 24 98 00 00 00 45 89 e6 41 83 e6 03 bf 02 00 00 00 4c 89 f6 e8 58 de be ff 4c 89 e6 4c 21 fe 31 db 31 ff e8 49 de be ff <4d> 21 e7 0f 84 97 00 00 00 49 81 fc 06 c0 ff ff 0f 82 8a 00 00 00
RSP: 0018:ffffc9000ae473a0 EFLAGS: 00000297
RAX: ffffffff82016f47 RBX: 0000000000000000 RCX: ffff88807b530000
RDX: 0000000000000002 RSI: 000000005545b9c0 RDI: 0000000000000000
RBP: ffffc9000ae474d0 R08: ffffffff8fa132f7 R09: 1ffffffff1f4265e
R10: dffffc0000000000 R11: fffffbfff1f4265f R12: ffff88805545b9c0
R13: 0000000000000cc0 R14: 0000000000000000 R15: 00000003fffffffc
 shmem_alloc_and_add_folio+0x846/0xf60 mm/shmem.c:1916
 shmem_get_folio_gfp+0x59d/0x1660 mm/shmem.c:2532
 shmem_fault+0x179/0x390 mm/shmem.c:2733
 __do_fault+0x135/0x390 mm/memory.c:5187
 do_read_fault mm/memory.c:5608 [inline]
 do_fault mm/memory.c:5742 [inline]
 do_pte_missing mm/memory.c:4249 [inline]
 handle_pte_fault mm/memory.c:6087 [inline]
 __handle_mm_fault+0x37ed/0x5620 mm/memory.c:6230
 handle_mm_fault+0x40a/0x8e0 mm/memory.c:6399
 faultin_page mm/gup.c:1186 [inline]
 __get_user_pages+0x1af4/0x30b0 mm/gup.c:1488
 populate_vma_page_range+0x26b/0x340 mm/gup.c:1926
 __mm_populate+0x24c/0x380 mm/gup.c:2029
 mm_populate include/linux/mm.h:3349 [inline]
 vm_mmap_pgoff+0x3f0/0x4c0 mm/util.c:584
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6aea98e969
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6aeb88f038 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007f6aeabb6080 RCX: 00007f6aea98e969
RDX: b635773f06ebbeef RSI: 0000000000b36000 RDI: 0000200000000000
RBP: 00007f6aeaa10ab1 R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000008031 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f6aeabb6080 R15: 00007fffd7a7e288
 </TASK>
----------------
Code disassembly (best guess):
   0:	8b a4 24 98 00 00 00 	mov    0x98(%rsp),%esp
   7:	45 89 e6             	mov    %r12d,%r14d
   a:	41 83 e6 03          	and    $0x3,%r14d
   e:	bf 02 00 00 00       	mov    $0x2,%edi
  13:	4c 89 f6             	mov    %r14,%rsi
  16:	e8 58 de be ff       	call   0xffbede73
  1b:	4c 89 e6             	mov    %r12,%rsi
  1e:	4c 21 fe             	and    %r15,%rsi
  21:	31 db                	xor    %ebx,%ebx
  23:	31 ff                	xor    %edi,%edi
  25:	e8 49 de be ff       	call   0xffbede73
* 2a:	4d 21 e7             	and    %r12,%r15 <-- trapping instruction
  2d:	0f 84 97 00 00 00    	je     0xca
  33:	49 81 fc 06 c0 ff ff 	cmp    $0xffffffffffffc006,%r12
  3a:	0f 82 8a 00 00 00    	jb     0xca