[moderation] [afs?] [net?] WARNING: refcount bug in rxrpc_get_connection
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syzbot
Aug 4, 2026, 8:13:38 PM (19 hours ago) Aug 4
to syzkaller-upst...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: 8ba098e6b6ff Merge tag 'v7.2-rc5-smb3-client-fixes' of git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16a24e32580000
kernel config: https://syzkaller.appspot.com/x/.config?x=145fa60d73086782
dashboard link: https://syzkaller.appspot.com/bug?extid=13186170c20865d82f91
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
CC: [da...@davemloft.net dhow...@redhat.com edum...@google.com ho...@kernel.org ku...@kernel.org linu...@lists.infradead.org linux-...@vger.kernel.org marc....@auristor.com net...@vger.kernel.org pab...@redhat.com]
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/db1d2f27959e/disk-8ba098e6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2eacbf7835c3/vmlinux-8ba098e6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/de833d39bd28/bzImage-8ba098e6.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+131861...@syzkaller.appspotmail.com
------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: lib/refcount.c:25 at refcount_warn_saturate+0x111/0x130 lib/refcount.c:25, CPU#0: syz.7.10144/5848
Modules linked in:
CPU: 0 UID: 0 PID: 5848 Comm: syz.7.10144 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:refcount_warn_saturate+0x111/0x130 lib/refcount.c:25
Code: cc e8 63 3a ec fc 48 8d 3d 6c 5e 0f 0c 67 48 0f b9 3a e8 52 3a ec fc 5b 5d e9 4b bb a0 06 e8 46 3a ec fc 48 8d 3d 5f 5e 0f 0c <67> 48 0f b9 3a e8 35 3a ec fc 5b 5d c3 cc cc cc cc 48 89 df e8 06
RSP: 0018:ffffc90000007bc8 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff888040b2f038 RCX: ffffffff851e26eb
RDX: ffff888021b04a80 RSI: ffffffff851e279a RDI: ffffffff912d8600
RBP: 0000000000000002 R08: 0000000000000005 R09: 0000000000000004
R10: 0000000000000002 R11: 0000000000000001 R12: 0000000000000009
R13: 0000000000000001 R14: ffff888040b2f038 R15: 0000000000000001
FS: 000055557e548500(0000) GS:ffff888123dda000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c38ed7a CR3: 0000000074082000 CR4: 00000000003526f0
Call Trace:
<IRQ>
__refcount_add include/linux/refcount.h:289 [inline]
__refcount_inc include/linux/refcount.h:366 [inline]
rxrpc_get_connection+0xef/0x100 net/rxrpc/conn_object.c:251
rxrpc_poke_conn+0xf7/0x240 net/rxrpc/conn_object.c:37
call_timer_fn+0x19a/0x610 kernel/time/timer.c:1748
expire_timers kernel/time/timer.c:1799 [inline]
__run_timers+0x757/0xb00 kernel/time/timer.c:2374
__run_timer_base kernel/time/timer.c:2386 [inline]
__run_timer_base kernel/time/timer.c:2378 [inline]
run_timer_base+0x114/0x190 kernel/time/timer.c:2395
run_timer_softirq+0x1a/0x50 kernel/time/timer.c:2405
handle_softirqs+0x1ea/0x9b0 kernel/softirq.c:622
__do_softirq kernel/softirq.c:656 [inline]
invoke_softirq kernel/softirq.c:496 [inline]
__irq_exit_rcu+0x162/0x210 kernel/softirq.c:735
irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa3/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:preempt_schedule_irq+0x4b/0x90 kernel/sched/core.c:7556
Code: 00 00 00 fc ff df 48 89 eb 48 c1 eb 03 48 01 d3 f6 c4 02 75 47 bf 01 00 00 00 e8 30 d1 18 f6 e8 7b ca 55 f6 fb bf 01 00 00 00 <e8> a0 91 ff ff 9c 58 fa f6 c4 02 75 1e bf 01 00 00 00 e8 1e 71 18
RSP: 0018:ffffc90003e87948 EFLAGS: 00000202
RAX: 000000000000826b RBX: ffffed1004360950 RCX: 0000000000000040
RDX: 0000000000000000 RSI: ffffffff8e1a76e9 RDI: 0000000000000001
RBP: ffff888021b04a80 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
irqentry_exit_to_kernel_mode_preempt include/linux/irq-entry-common.h:468 [inline]
irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline]
irqentry_exit+0x205/0xa00 kernel/entry/common.c:167
asm_sysvec_reschedule_ipi+0x1a/0x20 arch/x86/include/asm/idtentry.h:679
RIP: 0010:lockdep_unregister_key+0x12b/0x1d0 kernel/locking/lockdep.c:6616
Code: e8 da dd ff ff 48 83 2d 5a 88 9e 14 01 89 c3 e8 2b e0 ff ff 9c 58 f6 c4 02 0f 85 8a 00 00 00 f7 c5 00 02 00 00 74 01 fb 84 db <75> 40 5b 5d 41 5c e9 fa a8 09 00 9c 58 f6 c4 02 0f 84 16 ff ff ff
RSP: 0018:ffffc90003e87a50 EFLAGS: 00000246
RAX: 0000000000000046 RBX: 0000000000000000 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffff8e29db9c RDI: ffffffff8c402680
RBP: 0000000000000246 R08: 000000000008ab94 R09: ffffffff96958588
R10: 0000000000000200 R11: 0000000000000000 R12: ffffffff97eb2ec8
R13: ffff88804fa48000 R14: ffff88804fa48568 R15: 0000000000000100
qdisc_lock_uninit include/net/pkt_sched.h:332 [inline]
__qdisc_destroy+0x172/0x530 net/sched/sch_generic.c:1124
qdisc_put+0xb0/0xf0 net/sched/sch_generic.c:1150
shutdown_scheduler_queue+0xa5/0x160 net/sched/sch_generic.c:1203
netdev_for_each_tx_queue include/linux/netdevice.h:2735 [inline]
dev_shutdown+0xb3/0x440 net/sched/sch_generic.c:1512
unregister_netdevice_many_notify+0xd55/0x2140 net/core/dev.c:12434
unregister_netdevice_many net/core/dev.c:12507 [inline]
unregister_netdevice_queue net/core/dev.c:12319 [inline]
unregister_netdevice_queue+0x30b/0x3c0 net/core/dev.c:12309
unregister_netdevice include/linux/netdevice.h:3472 [inline]
__tun_detach+0x1173/0x1480 drivers/net/tun.c:621
tun_detach drivers/net/tun.c:637 [inline]
tun_chr_close+0xc2/0x220 drivers/net/tun.c:3442
__fput+0x3ff/0xb50 fs/file_table.c:512
task_work_run+0x150/0x240 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:70 [inline]
exit_to_user_mode_loop+0x1d8/0x6f0 kernel/entry/common.c:101
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
do_syscall_64+0x666/0x870 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb9a859e019
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff6e3ae3e8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fff6e3ae4d0 RCX: 00007fb9a859e019
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00000000001873db R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b2ce20000 R11: 0000000000000246 R12: 00007fff6e3ae510
R13: 00007fb9a8825fac R14: 0000000000187458 R15: 00007fb9a8825fa0
</TASK>
----------------
Code disassembly (best guess):
0: cc int3
1: e8 63 3a ec fc call 0xfcec3a69
6: 48 8d 3d 6c 5e 0f 0c lea 0xc0f5e6c(%rip),%rdi # 0xc0f5e79
d: 67 48 0f b9 3a ud1 (%edx),%rdi
12: e8 52 3a ec fc call 0xfcec3a69
17: 5b pop %rbx
18: 5d pop %rbp
19: e9 4b bb a0 06 jmp 0x6a0bb69
1e: e8 46 3a ec fc call 0xfcec3a69
23: 48 8d 3d 5f 5e 0f 0c lea 0xc0f5e5f(%rip),%rdi # 0xc0f5e89
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: e8 35 3a ec fc call 0xfcec3a69
34: 5b pop %rbx
35: 5d pop %rbp
36: c3 ret
37: cc int3
38: cc int3
39: cc int3
3a: cc int3
3b: 48 89 df mov %rbx,%rdi
3e: e8 .byte 0xe8
3f: 06 (bad)
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
syzbot found the following issue on:
HEAD commit: 8ba098e6b6ff Merge tag 'v7.2-rc5-smb3-client-fixes' of git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16a24e32580000
kernel config: https://syzkaller.appspot.com/x/.config?x=145fa60d73086782
dashboard link: https://syzkaller.appspot.com/bug?extid=13186170c20865d82f91
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
CC: [da...@davemloft.net dhow...@redhat.com edum...@google.com ho...@kernel.org ku...@kernel.org linu...@lists.infradead.org linux-...@vger.kernel.org marc....@auristor.com net...@vger.kernel.org pab...@redhat.com]
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/db1d2f27959e/disk-8ba098e6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2eacbf7835c3/vmlinux-8ba098e6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/de833d39bd28/bzImage-8ba098e6.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+131861...@syzkaller.appspotmail.com
------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: lib/refcount.c:25 at refcount_warn_saturate+0x111/0x130 lib/refcount.c:25, CPU#0: syz.7.10144/5848
Modules linked in:
CPU: 0 UID: 0 PID: 5848 Comm: syz.7.10144 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:refcount_warn_saturate+0x111/0x130 lib/refcount.c:25
Code: cc e8 63 3a ec fc 48 8d 3d 6c 5e 0f 0c 67 48 0f b9 3a e8 52 3a ec fc 5b 5d e9 4b bb a0 06 e8 46 3a ec fc 48 8d 3d 5f 5e 0f 0c <67> 48 0f b9 3a e8 35 3a ec fc 5b 5d c3 cc cc cc cc 48 89 df e8 06
RSP: 0018:ffffc90000007bc8 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff888040b2f038 RCX: ffffffff851e26eb
RDX: ffff888021b04a80 RSI: ffffffff851e279a RDI: ffffffff912d8600
RBP: 0000000000000002 R08: 0000000000000005 R09: 0000000000000004
R10: 0000000000000002 R11: 0000000000000001 R12: 0000000000000009
R13: 0000000000000001 R14: ffff888040b2f038 R15: 0000000000000001
FS: 000055557e548500(0000) GS:ffff888123dda000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c38ed7a CR3: 0000000074082000 CR4: 00000000003526f0
Call Trace:
<IRQ>
__refcount_add include/linux/refcount.h:289 [inline]
__refcount_inc include/linux/refcount.h:366 [inline]
rxrpc_get_connection+0xef/0x100 net/rxrpc/conn_object.c:251
rxrpc_poke_conn+0xf7/0x240 net/rxrpc/conn_object.c:37
call_timer_fn+0x19a/0x610 kernel/time/timer.c:1748
expire_timers kernel/time/timer.c:1799 [inline]
__run_timers+0x757/0xb00 kernel/time/timer.c:2374
__run_timer_base kernel/time/timer.c:2386 [inline]
__run_timer_base kernel/time/timer.c:2378 [inline]
run_timer_base+0x114/0x190 kernel/time/timer.c:2395
run_timer_softirq+0x1a/0x50 kernel/time/timer.c:2405
handle_softirqs+0x1ea/0x9b0 kernel/softirq.c:622
__do_softirq kernel/softirq.c:656 [inline]
invoke_softirq kernel/softirq.c:496 [inline]
__irq_exit_rcu+0x162/0x210 kernel/softirq.c:735
irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa3/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:preempt_schedule_irq+0x4b/0x90 kernel/sched/core.c:7556
Code: 00 00 00 fc ff df 48 89 eb 48 c1 eb 03 48 01 d3 f6 c4 02 75 47 bf 01 00 00 00 e8 30 d1 18 f6 e8 7b ca 55 f6 fb bf 01 00 00 00 <e8> a0 91 ff ff 9c 58 fa f6 c4 02 75 1e bf 01 00 00 00 e8 1e 71 18
RSP: 0018:ffffc90003e87948 EFLAGS: 00000202
RAX: 000000000000826b RBX: ffffed1004360950 RCX: 0000000000000040
RDX: 0000000000000000 RSI: ffffffff8e1a76e9 RDI: 0000000000000001
RBP: ffff888021b04a80 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
irqentry_exit_to_kernel_mode_preempt include/linux/irq-entry-common.h:468 [inline]
irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline]
irqentry_exit+0x205/0xa00 kernel/entry/common.c:167
asm_sysvec_reschedule_ipi+0x1a/0x20 arch/x86/include/asm/idtentry.h:679
RIP: 0010:lockdep_unregister_key+0x12b/0x1d0 kernel/locking/lockdep.c:6616
Code: e8 da dd ff ff 48 83 2d 5a 88 9e 14 01 89 c3 e8 2b e0 ff ff 9c 58 f6 c4 02 0f 85 8a 00 00 00 f7 c5 00 02 00 00 74 01 fb 84 db <75> 40 5b 5d 41 5c e9 fa a8 09 00 9c 58 f6 c4 02 0f 84 16 ff ff ff
RSP: 0018:ffffc90003e87a50 EFLAGS: 00000246
RAX: 0000000000000046 RBX: 0000000000000000 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffff8e29db9c RDI: ffffffff8c402680
RBP: 0000000000000246 R08: 000000000008ab94 R09: ffffffff96958588
R10: 0000000000000200 R11: 0000000000000000 R12: ffffffff97eb2ec8
R13: ffff88804fa48000 R14: ffff88804fa48568 R15: 0000000000000100
qdisc_lock_uninit include/net/pkt_sched.h:332 [inline]
__qdisc_destroy+0x172/0x530 net/sched/sch_generic.c:1124
qdisc_put+0xb0/0xf0 net/sched/sch_generic.c:1150
shutdown_scheduler_queue+0xa5/0x160 net/sched/sch_generic.c:1203
netdev_for_each_tx_queue include/linux/netdevice.h:2735 [inline]
dev_shutdown+0xb3/0x440 net/sched/sch_generic.c:1512
unregister_netdevice_many_notify+0xd55/0x2140 net/core/dev.c:12434
unregister_netdevice_many net/core/dev.c:12507 [inline]
unregister_netdevice_queue net/core/dev.c:12319 [inline]
unregister_netdevice_queue+0x30b/0x3c0 net/core/dev.c:12309
unregister_netdevice include/linux/netdevice.h:3472 [inline]
__tun_detach+0x1173/0x1480 drivers/net/tun.c:621
tun_detach drivers/net/tun.c:637 [inline]
tun_chr_close+0xc2/0x220 drivers/net/tun.c:3442
__fput+0x3ff/0xb50 fs/file_table.c:512
task_work_run+0x150/0x240 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:70 [inline]
exit_to_user_mode_loop+0x1d8/0x6f0 kernel/entry/common.c:101
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
do_syscall_64+0x666/0x870 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb9a859e019
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff6e3ae3e8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fff6e3ae4d0 RCX: 00007fb9a859e019
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00000000001873db R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b2ce20000 R11: 0000000000000246 R12: 00007fff6e3ae510
R13: 00007fb9a8825fac R14: 0000000000187458 R15: 00007fb9a8825fa0
</TASK>
----------------
Code disassembly (best guess):
0: cc int3
1: e8 63 3a ec fc call 0xfcec3a69
6: 48 8d 3d 6c 5e 0f 0c lea 0xc0f5e6c(%rip),%rdi # 0xc0f5e79
d: 67 48 0f b9 3a ud1 (%edx),%rdi
12: e8 52 3a ec fc call 0xfcec3a69
17: 5b pop %rbx
18: 5d pop %rbp
19: e9 4b bb a0 06 jmp 0x6a0bb69
1e: e8 46 3a ec fc call 0xfcec3a69
23: 48 8d 3d 5f 5e 0f 0c lea 0xc0f5e5f(%rip),%rdi # 0xc0f5e89
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: e8 35 3a ec fc call 0xfcec3a69
34: 5b pop %rbx
35: 5d pop %rbp
36: c3 ret
37: cc int3
38: cc int3
39: cc int3
3a: cc int3
3b: 48 89 df mov %rbx,%rdi
3e: e8 .byte 0xe8
3f: 06 (bad)
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
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