================================================================== BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline] BUG: KASAN: use-after-free in atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:167 [inline] BUG: KASAN: use-after-free in __refcount_sub_and_test include/linux/refcount.h:272 [inline] BUG: KASAN: use-after-free in __refcount_dec_and_test include/linux/refcount.h:315 [inline] BUG: KASAN: use-after-free in refcount_dec_and_test include/linux/refcount.h:333 [inline] BUG: KASAN: use-after-free in ax25_dev_put include/net/ax25.h:301 [inline] BUG: KASAN: use-after-free in ax25_dev_device_down+0x354/0x67c net/ax25/ax25_dev.c:122 Write of size 4 at addr ffff0000c8f162b8 by task syz.1.249/4952 CPU: 0 PID: 4952 Comm: syz.1.249 Not tainted 5.15.189-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call trace: dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216 __dump_stack+0x30/0x40 lib/dump_stack.c:88 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106 print_address_description+0x78/0x30c mm/kasan/report.c:248 __kasan_report mm/kasan/report.c:434 [inline] kasan_report+0xec/0x15c mm/kasan/report.c:451 check_region_inline mm/kasan/generic.c:-1 [inline] kasan_check_range+0x270/0x2b0 mm/kasan/generic.c:189 __kasan_check_write+0x44/0x54 mm/kasan/shadow.c:37 instrument_atomic_read_write include/linux/instrumented.h:101 [inline] atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:167 [inline] __refcount_sub_and_test include/linux/refcount.h:272 [inline] __refcount_dec_and_test include/linux/refcount.h:315 [inline] refcount_dec_and_test include/linux/refcount.h:333 [inline] ax25_dev_put include/net/ax25.h:301 [inline] ax25_dev_device_down+0x354/0x67c net/ax25/ax25_dev.c:122 ax25_device_event+0x538/0x590 net/ax25/af_ax25.c:144 notifier_call_chain kernel/notifier.c:83 [inline] raw_notifier_call_chain+0xd4/0x164 kernel/notifier.c:391 call_netdevice_notifiers_info net/core/dev.c:2049 [inline] call_netdevice_notifiers_extack net/core/dev.c:2061 [inline] call_netdevice_notifiers net/core/dev.c:2075 [inline] __dev_notify_flags+0x250/0x46c net/core/dev.c:-1 dev_change_flags+0xc8/0x154 net/core/dev.c:8929 dev_ifsioc+0x504/0xef4 net/core/dev_ioctl.c:324 dev_ioctl+0x4d0/0xc94 net/core/dev_ioctl.c:587 sock_do_ioctl+0x18c/0x240 net/socket.c:1154 sock_ioctl+0x5c8/0x87c net/socket.c:1257 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 Allocated by task 4625: kasan_save_stack mm/kasan/common.c:38 [inline] kasan_set_track mm/kasan/common.c:46 [inline] set_alloc_info mm/kasan/common.c:434 [inline] ____kasan_kmalloc mm/kasan/common.c:513 [inline] __kasan_kmalloc+0xb0/0xf0 mm/kasan/common.c:522 kasan_kmalloc include/linux/kasan.h:264 [inline] kmem_cache_alloc_trace+0x274/0x3fc mm/slub.c:3247 kmalloc include/linux/slab.h:604 [inline] kzalloc include/linux/slab.h:735 [inline] ax25_dev_device_up+0x5c/0x540 net/ax25/ax25_dev.c:55 ax25_device_event+0x504/0x590 net/ax25/af_ax25.c:139 notifier_call_chain kernel/notifier.c:83 [inline] raw_notifier_call_chain+0xd4/0x164 kernel/notifier.c:391 call_netdevice_notifiers_info net/core/dev.c:2049 [inline] call_netdevice_notifiers_extack net/core/dev.c:2061 [inline] call_netdevice_notifiers net/core/dev.c:2075 [inline] __dev_notify_flags+0x250/0x46c net/core/dev.c:-1 dev_change_flags+0xc8/0x154 net/core/dev.c:8929 dev_ifsioc+0x504/0xef4 net/core/dev_ioctl.c:324 dev_ioctl+0x4d0/0xc94 net/core/dev_ioctl.c:587 sock_do_ioctl+0x18c/0x240 net/socket.c:1154 sock_ioctl+0x5c8/0x87c net/socket.c:1257 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 Freed by task 4952: kasan_save_stack mm/kasan/common.c:38 [inline] kasan_set_track+0x4c/0x84 mm/kasan/common.c:46 kasan_set_free_info+0x28/0x4c mm/kasan/generic.c:360 ____kasan_slab_free+0x118/0x164 mm/kasan/common.c:366 __kasan_slab_free+0x18/0x28 mm/kasan/common.c:374 kasan_slab_free include/linux/kasan.h:230 [inline] slab_free_hook mm/slub.c:1705 [inline] slab_free_freelist_hook+0x128/0x1e8 mm/slub.c:1731 slab_free mm/slub.c:3499 [inline] kfree+0x170/0x40c mm/slub.c:4559 ax25_dev_put include/net/ax25.h:302 [inline] ax25_dev_device_down+0x1ac/0x67c net/ax25/ax25_dev.c:119 ax25_device_event+0x538/0x590 net/ax25/af_ax25.c:144 notifier_call_chain kernel/notifier.c:83 [inline] raw_notifier_call_chain+0xd4/0x164 kernel/notifier.c:391 call_netdevice_notifiers_info net/core/dev.c:2049 [inline] call_netdevice_notifiers_extack net/core/dev.c:2061 [inline] call_netdevice_notifiers net/core/dev.c:2075 [inline] __dev_notify_flags+0x250/0x46c net/core/dev.c:-1 dev_change_flags+0xc8/0x154 net/core/dev.c:8929 dev_ifsioc+0x504/0xef4 net/core/dev_ioctl.c:324 dev_ioctl+0x4d0/0xc94 net/core/dev_ioctl.c:587 sock_do_ioctl+0x18c/0x240 net/socket.c:1154 sock_ioctl+0x5c8/0x87c net/socket.c:1257 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 Last potentially related work creation: kasan_save_stack+0x38/0x68 mm/kasan/common.c:38 kasan_record_aux_stack+0xcc/0x114 mm/kasan/generic.c:348 kvfree_call_rcu+0xb8/0x66c kernel/rcu/tree.c:3600 subflow_ulp_release+0x224/0x2ec net/mptcp/subflow.c:1750 tcp_cleanup_ulp+0x74/0xec net/ipv4/tcp_ulp.c:124 tcp_v4_destroy_sock+0x1c8/0x6dc net/ipv4/tcp_ipv4.c:2300 inet_csk_destroy_sock+0x148/0x400 net/ipv4/inet_connection_sock.c:1051 __tcp_close+0xb94/0x104c net/ipv4/tcp.c:2910 __mptcp_close_ssk+0x1e4/0x4a4 net/mptcp/protocol.c:2330 __mptcp_destroy_sock+0x2ec/0x610 net/mptcp/protocol.c:2763 mptcp_close+0x5b8/0xa04 net/mptcp/protocol.c:2820 inet_release+0x120/0x16c net/ipv4/af_inet.c:432 inet6_release+0x5c/0x78 net/ipv6/af_inet6.c:490 __sock_release net/socket.c:649 [inline] sock_close+0xb4/0x1f8 net/socket.c:1336 __fput+0x1c0/0x7f8 fs/file_table.c:311 ____fput+0x20/0x30 fs/file_table.c:339 task_work_run+0x12c/0x1e0 kernel/task_work.c:188 tracehook_notify_resume include/linux/tracehook.h:189 [inline] do_notify_resume+0x24b4/0x3128 arch/arm64/kernel/signal.c:949 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:133 [inline] exit_to_user_mode arch/arm64/kernel/entry-common.c:138 [inline] el0_svc+0xf0/0x1e0 arch/arm64/kernel/entry-common.c:609 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 The buggy address belongs to the object at ffff0000c8f16200 which belongs to the cache kmalloc-256 of size 256 The buggy address is located 184 bytes inside of 256-byte region [ffff0000c8f16200, ffff0000c8f16300) The buggy address belongs to the page: page:00000000cc65b723 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff0000c8f17200 pfn:0x108f16 head:00000000cc65b723 order:1 compound_mapcount:0 flags: 0x5ffc00000010200(slab|head|node=0|zone=2|lastcpupid=0x7ff) raw: 05ffc00000010200 fffffc0003467580 0000000c00000007 ffff0000c0002480 raw: ffff0000c8f17200 000000008010000f 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff0000c8f16180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff0000c8f16200: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff0000c8f16280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff0000c8f16300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff0000c8f16380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 1 PID: 4952 at lib/refcount.c:28 refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28 Modules linked in: CPU: 1 PID: 4952 Comm: syz.1.249 Tainted: G B 5.15.189-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28 lr : refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28 sp : ffff800021c37690 x29: ffff800021c37690 x28: ffff8000163d4b00 x27: 1fffe000191e2c42 x26: ffff80001b1e4000 x25: 1fffe0001a2fe86d x24: dfff800000000000 x23: 0000000000000001 x22: ffff0000c8f162b8 x21: 0000000000000007 x20: ffff0000c8f162b8 x19: ffff8000165b2000 x18: 0000000000000000 x17: 0000000000000002 x16: ffff8000111bc798 x15: 0000000000000012 x14: 0000000000ff0100 x13: 0a2e656572662d72 x12: 0000000000080000 x11: 0000000000039e81 x10: ffff800025299000 x9 : d9d3249ab1609c00 x8 : d9d3249ab1609c00 x7 : 0000000000000000 x6 : ffff8000082f6fc4 x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff80000850433c x2 : 0000000000000001 x1 : 0000000100000000 x0 : 0000000000000026 Call trace: refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28 __refcount_sub_and_test include/linux/refcount.h:283 [inline] __refcount_dec_and_test include/linux/refcount.h:315 [inline] refcount_dec_and_test include/linux/refcount.h:333 [inline] ax25_dev_put include/net/ax25.h:301 [inline] ax25_dev_device_down+0x528/0x67c net/ax25/ax25_dev.c:-1 ax25_device_event+0x538/0x590 net/ax25/af_ax25.c:144 notifier_call_chain kernel/notifier.c:83 [inline] raw_notifier_call_chain+0xd4/0x164 kernel/notifier.c:391 call_netdevice_notifiers_info net/core/dev.c:2049 [inline] call_netdevice_notifiers_extack net/core/dev.c:2061 [inline] call_netdevice_notifiers net/core/dev.c:2075 [inline] __dev_notify_flags+0x250/0x46c net/core/dev.c:-1 dev_change_flags+0xc8/0x154 net/core/dev.c:8929 dev_ifsioc+0x504/0xef4 net/core/dev_ioctl.c:324 dev_ioctl+0x4d0/0xc94 net/core/dev_ioctl.c:587 sock_do_ioctl+0x18c/0x240 net/socket.c:1154 sock_ioctl+0x5c8/0x87c net/socket.c:1257 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 irq event stamp: 524 hardirqs last enabled at (523): [] kasan_quarantine_put+0xc4/0x204 mm/kasan/quarantine.c:231 hardirqs last disabled at (524): [] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:108 [inline] hardirqs last disabled at (524): [] _raw_spin_lock_irqsave+0xfc/0x14c kernel/locking/spinlock.c:162 softirqs last enabled at (516): [] spin_unlock_bh include/linux/spinlock.h:408 [inline] softirqs last enabled at (516): [] ax25_dev_device_down+0x160/0x67c net/ax25/ax25_dev.c:118 softirqs last disabled at (512): [] spin_lock_bh include/linux/spinlock.h:368 [inline] softirqs last disabled at (512): [] ax25_dev_device_down+0x64/0x67c net/ax25/ax25_dev.c:103 ---[ end trace 52087bc50e1f65cb ]---