==================================================================
BUG: KASAN: use-after-free in ax25_heartbeat_expiry+0x10c/0x130 net/ax25/ax25_timer.c:125
Read of size 4 at addr ffff8880746bef50 by task syz.4.50/4414

CPU: 0 PID: 4414 Comm: syz.4.50 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <IRQ>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 ax25_heartbeat_expiry+0x10c/0x130 net/ax25/ax25_timer.c:125
 call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648
 expire_timers kernel/time/timer.c:1699 [inline]
 __run_timers+0x53e/0x800 kernel/time/timer.c:1970
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1983
 handle_softirqs+0x339/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:lock_acquire+0x208/0x400 kernel/locking/lockdep.c:5627
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3d 04 f8 0f 85 f1 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 44 3d 00 00 00 00 00 43 c7 44 3d 08 00 00 00 00 65 48 8b 04
RSP: 0018:ffffc90003147480 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 43c133c1bb046b00
RDX: 0000000000000000 RSI: ffffffff8a2b3a20 RDI: ffffffff8a79f980
RBP: ffffc90003147588 R08: dffffc0000000000 R09: 1ffffffff203a82e
R10: dffffc0000000000 R11: fffffbfff203a82f R12: ffff88801b7dfda0
R13: 1ffff92000628e9c R14: 0000000000000246 R15: dffffc0000000000
 __mutex_lock_common+0x1e3/0x2400 kernel/locking/mutex.c:596
 __mutex_lock kernel/locking/mutex.c:729 [inline]
 mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
 __unix_dgram_recvmsg+0x205/0xd90 net/unix/af_unix.c:2312
 ____sys_recvmsg+0x2cd/0x5e0 net/socket.c:-1
 ___sys_recvmsg+0x21a/0x5c0 net/socket.c:2706
 do_recvmmsg+0x382/0x850 net/socket.c:2800
 __sys_recvmmsg net/socket.c:2879 [inline]
 __do_sys_recvmmsg net/socket.c:2902 [inline]
 __se_sys_recvmmsg net/socket.c:2895 [inline]
 __x64_sys_recvmmsg+0x195/0x250 net/socket.c:2895
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fd448506799
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:00007fd44673f028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007fd448780090 RCX: 00007fd448506799
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000005
RBP: 00007fd44859cc99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd448780128 R14: 00007fd448780090 R15: 00007ffecb571df8
 </TASK>

Allocated by task 4334:
 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+0xb5/0xf0 mm/kasan/common.c:522
 kmalloc include/linux/slab.h:607 [inline]
 kzalloc include/linux/slab.h:738 [inline]
 ax25_dev_device_up+0x50/0x580 net/ax25/ax25_dev.c:55
 ax25_device_event+0x483/0x4f0 net/ax25/af_ax25.c:139
 notifier_call_chain kernel/notifier.c:83 [inline]
 raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:391
 call_netdevice_notifiers_extack net/core/dev.c:2074 [inline]
 call_netdevice_notifiers net/core/dev.c:2088 [inline]
 __dev_notify_flags+0x194/0x300 net/core/dev.c:8917
 dev_change_flags+0xe3/0x1a0 net/core/dev.c:8955
 dev_ifsioc+0x130/0xd50 net/core/dev_ioctl.c:324
 dev_ioctl+0x545/0xe30 net/core/dev_ioctl.c:572
 sock_do_ioctl+0x245/0x320 net/socket.c:1161
 sock_ioctl+0x4d2/0x710 net/socket.c:1266
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Freed by task 4381:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
 ____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:1710 [inline]
 slab_free_freelist_hook+0xea/0x170 mm/slub.c:1736
 slab_free mm/slub.c:3504 [inline]
 kfree+0xef/0x2a0 mm/slub.c:4564
 ax25_dev_put include/net/ax25.h:302 [inline]
 ax25_release+0x661/0x870 net/ax25/af_ax25.c:1062
 __sock_release net/socket.c:651 [inline]
 sock_close+0xd5/0x240 net/socket.c:1345
 __fput+0x234/0x930 fs/file_table.c:311
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 get_signal+0x1222/0x12c0 kernel/signal.c:2672
 arch_do_signal_or_restart+0xe7/0x12c0 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

The buggy address belongs to the object at ffff8880746bef00
 which belongs to the cache kmalloc-192 of size 192
The buggy address is located 80 bytes inside of
 192-byte region [ffff8880746bef00, ffff8880746befc0)
The buggy address belongs to the page:
page:ffffea0001d1af80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x746be
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 0000000000000000 dead000000000122 ffff888016c41a00
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 4321, ts 81678040216, free_ts 81496104064
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x1bbd/0x1ca0 mm/page_alloc.c:4192
 __alloc_pages+0x1ee/0x480 mm/page_alloc.c:5501
 __alloc_pages_node include/linux/gfp.h:570 [inline]
 alloc_slab_page mm/slub.c:1782 [inline]
 allocate_slab mm/slub.c:1917 [inline]
 new_slab+0xb6/0x4b0 mm/slub.c:1980
 ___slab_alloc+0x80a/0xdd0 mm/slub.c:3013
 __slab_alloc mm/slub.c:3100 [inline]
 slab_alloc_node mm/slub.c:3191 [inline]
 __kmalloc_node+0x200/0x3b0 mm/slub.c:4456
 kmalloc_array_node include/linux/slab.h:700 [inline]
 kcalloc_node include/linux/slab.h:705 [inline]
 memcg_alloc_page_obj_cgroups+0x81/0x120 mm/memcontrol.c:2839
 account_slab_page mm/slab.h:424 [inline]
 allocate_slab mm/slub.c:1933 [inline]
 new_slab+0x100/0x4b0 mm/slub.c:1980
 ___slab_alloc+0x80a/0xdd0 mm/slub.c:3013
 __slab_alloc mm/slub.c:3100 [inline]
 slab_alloc_node mm/slub.c:3191 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 kmem_cache_alloc+0x195/0x290 mm/slub.c:3238
 sock_alloc_inode+0x17/0xb0 net/socket.c:305
 alloc_inode fs/inode.c:261 [inline]
 new_inode_pseudo+0x5f/0x210 fs/inode.c:1001
 sock_alloc net/socket.c:628 [inline]
 __sock_create+0x129/0x900 net/socket.c:1459
 sock_create net/socket.c:1551 [inline]
 __sys_socketpair+0x232/0x540 net/socket.c:1655
 __do_sys_socketpair net/socket.c:1704 [inline]
 __se_sys_socketpair net/socket.c:1701 [inline]
 __x64_sys_socketpair+0x97/0xb0 net/socket.c:1701
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
 free_unref_page_list+0x119/0x820 mm/page_alloc.c:3433
 release_pages+0x186c/0x1be0 mm/swap.c:963
 tlb_batch_pages_flush mm/mmu_gather.c:49 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:240 [inline]
 tlb_flush_mmu mm/mmu_gather.c:247 [inline]
 tlb_finish_mmu+0x176/0x300 mm/mmu_gather.c:338
 exit_mmap+0x3d0/0x640 mm/mmap.c:3218
 __mmput+0x115/0x3b0 kernel/fork.c:1127
 exit_mm+0x588/0x6e0 kernel/exit.c:550
 do_exit+0x5a9/0x20c0 kernel/exit.c:870
 do_group_exit+0x12e/0x300 kernel/exit.c:997
 get_signal+0x6ca/0x12c0 kernel/signal.c:2900
 arch_do_signal_or_restart+0xe7/0x12c0 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Memory state around the buggy address:
 ffff8880746bee00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880746bee80: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
>ffff8880746bef00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff8880746bef80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff8880746bf000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
----------------
Code disassembly (best guess):
   0:	f7 84 24 80 00 00 00 	testl  $0x200,0x80(%rsp)
   7:	00 02 00 00
   b:	43 c6 44 3d 04 f8    	movb   $0xf8,0x4(%r13,%r15,1)
  11:	0f 85 f1 00 00 00    	jne    0x108
  17:	41 f7 c6 00 02 00 00 	test   $0x200,%r14d
  1e:	74 01                	je     0x21
  20:	fb                   	sti
  21:	48 c7 44 24 60 0e 36 	movq   $0x45e0360e,0x60(%rsp)
  28:	e0 45
* 2a:	4b c7 44 3d 00 00 00 	movq   $0x0,0x0(%r13,%r15,1) <-- trapping instruction
  31:	00 00
  33:	43 c7 44 3d 08 00 00 	movl   $0x0,0x8(%r13,%r15,1)
  3a:	00 00
  3c:	65                   	gs
  3d:	48                   	rex.W
  3e:	8b                   	.byte 0x8b
  3f:	04                   	.byte 0x4