==================================================================
BUG: KASAN: use-after-free in ax25_heartbeat_expiry+0x10c/0x130 net/ax25/ax25_timer.c:127
Read of size 4 at addr ffff88802f5c9260 by task rm/10949

CPU: 0 PID: 10949 Comm: rm Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <IRQ>
 dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:420
 kasan_report+0x10b/0x140 mm/kasan/report.c:524
 ax25_heartbeat_expiry+0x10c/0x130 net/ax25/ax25_timer.c:127
 call_timer_fn+0x1a0/0x670 kernel/time/timer.c:1700
 expire_timers kernel/time/timer.c:1751 [inline]
 __run_timers+0x529/0x7d0 kernel/time/timer.c:2022
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:2035
 handle_softirqs+0x2a1/0x920 kernel/softirq.c:596
 __do_softirq kernel/softirq.c:630 [inline]
 invoke_softirq kernel/softirq.c:470 [inline]
 __irq_exit_rcu+0x12f/0x220 kernel/softirq.c:679
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:__kasan_check_write+0x6/0x10 mm/kasan/shadow.c:37
Code: d0 d7 43 8c 48 89 de e8 c8 be 3b 08 31 ed eb d7 00 00 cc cc 89 f6 48 8b 0c 24 31 d2 e9 a3 ec ff ff 0f 1f 00 89 f6 48 8b 0c 24 <ba> 01 00 00 00 e9 90 ec ff ff 55 41 56 53 48 89 d3 89 f5 49 89 fe
RSP: 0018:ffffc9000473f6d8 EFLAGS: 00000293
RAX: ffffffff8a059f89 RBX: 000055cddf8e8000 RCX: ffffffff8a05a025
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffffffff970584e0
RBP: ffffc9000473f8b0 R08: 0000000000000004 R09: 0000000000000003
R10: fffffbfff2e0b098 R11: 1ffffffff2e0b098 R12: 0000000000000000
R13: ffff88805f0240a0 R14: 000055cddf8e8000 R15: dffffc0000000000
 instrument_atomic_read_write include/linux/instrumented.h:102 [inline]
 atomic_inc include/linux/atomic/atomic-instrumented.h:190 [inline]
 mas_validate_gaps lib/maple_tree.c:7028 [inline]
 mt_validate+0x3815/0x4c90 lib/maple_tree.c:7244
 validate_mm_mt+0xcd/0x420 mm/mmap.c:295
 validate_mm+0xcc/0x2b0 mm/mmap.c:332
 mmap_region+0x780/0x1c70 mm/mmap.c:2922
 do_mmap+0x958/0xfd0 mm/mmap.c:1436
 vm_mmap_pgoff+0x1b2/0x2b0 mm/util.c:520
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f63ca728242
Code: 08 00 04 00 00 eb e2 90 41 f7 c1 ff 0f 00 00 75 27 55 89 cd 53 48 89 fb 48 85 ff 74 33 41 89 ea 48 89 df b8 09 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 5e 5b 5d c3 0f 1f 00 c7 05 46 40 01 00 16 00
RSP: 002b:00007ffd3debfbb8 EFLAGS: 00000206 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007f63ca635000 RCX: 00007f63ca728242
RDX: 0000000000000003 RSI: 000000000000ce98 RDI: 00007f63ca635000
RBP: 0000000000000032 R08: 00000000ffffffff R09: 0000000000000000
R10: 0000000000000032 R11: 0000000000000206 R12: 00007ffd3debfc78
R13: 00007f63ca7045f0 R14: 00007ffd3dec03f0 R15: 00007f63ca635000
 </TASK>

Allocated by task 10493:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0x8e/0xa0 mm/kasan/common.c:383
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 ax25_dev_device_up+0x50/0x5f0 net/ax25/ax25_dev.c:57
 ax25_device_event+0x117/0x600 net/ax25/af_ax25.c:143
 notifier_call_chain kernel/notifier.c:87 [inline]
 raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:455
 call_netdevice_notifiers_extack net/core/dev.c:2039 [inline]
 call_netdevice_notifiers net/core/dev.c:2053 [inline]
 __dev_notify_flags+0x178/0x2d0 net/core/dev.c:-1
 dev_change_flags+0xe3/0x1a0 net/core/dev.c:8714
 dev_ifsioc+0x159/0xe90 net/core/dev_ioctl.c:327
 dev_ioctl+0x578/0xea0 net/core/dev_ioctl.c:588
 sock_do_ioctl+0x222/0x2f0 net/socket.c:1218
 sock_ioctl+0x4ed/0x6e0 net/socket.c:1321
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 7379:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x2d/0x50 mm/kasan/generic.c:516
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1729 [inline]
 slab_free_freelist_hook+0x131/0x1a0 mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 kmem_cache_free_bulk+0x348/0x460 mm/slub.c:3805
 kfree_bulk include/linux/slab.h:475 [inline]
 kfree_rcu_work+0x33f/0x890 kernel/rcu/tree.c:3091
 process_one_work+0x898/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1250 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:45
 __kasan_record_aux_stack+0xb2/0xc0 mm/kasan/generic.c:486
 kvfree_call_rcu+0x108/0x870 kernel/rcu/tree.c:3405
 ax25_device_event+0x555/0x600 net/ax25/af_ax25.c:148
 notifier_call_chain kernel/notifier.c:87 [inline]
 raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:455
 call_netdevice_notifiers_extack net/core/dev.c:2039 [inline]
 call_netdevice_notifiers net/core/dev.c:2053 [inline]
 __dev_notify_flags+0x178/0x2d0 net/core/dev.c:-1
 dev_change_flags+0xe3/0x1a0 net/core/dev.c:8714
 dev_ifsioc+0x159/0xe90 net/core/dev_ioctl.c:327
 dev_ioctl+0x578/0xea0 net/core/dev_ioctl.c:588
 sock_do_ioctl+0x222/0x2f0 net/socket.c:1218
 sock_ioctl+0x4ed/0x6e0 net/socket.c:1321
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Second to last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:45
 __kasan_record_aux_stack+0xb2/0xc0 mm/kasan/generic.c:486
 kvfree_call_rcu+0x108/0x870 kernel/rcu/tree.c:3405
 drop_sysctl_table+0x2fa/0x430 fs/proc/proc_sysctl.c:1731
 drop_sysctl_table+0x2e9/0x430 fs/proc/proc_sysctl.c:1734
 unregister_sysctl_table+0x85/0x130 fs/proc/proc_sysctl.c:1769
 neigh_sysctl_unregister+0x74/0x90 net/core/neighbour.c:3877
 addrconf_sysctl_unregister net/ipv6/addrconf.c:7207 [inline]
 addrconf_ifdown+0x1711/0x1a10 net/ipv6/addrconf.c:3951
 addrconf_notify+0x405/0xf40 net/ipv6/addrconf.c:-1
 notifier_call_chain kernel/notifier.c:87 [inline]
 raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:455
 call_netdevice_notifiers_extack net/core/dev.c:2039 [inline]
 call_netdevice_notifiers net/core/dev.c:2053 [inline]
 unregister_netdevice_many+0xfdc/0x1840 net/core/dev.c:10990
 ip6gre_exit_batch_net+0x445/0x490 net/ipv6/ip6_gre.c:1670
 ops_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x77b/0xb80 net/core/net_namespace.c:640
 process_one_work+0x898/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1250 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

The buggy address belongs to the object at ffff88802f5c9200
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 96 bytes inside of
 256-byte region [ffff88802f5c9200, ffff88802f5c9300)

The buggy address belongs to the physical page:
page:ffffea0000bd7200 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88802f5c9600 pfn:0x2f5c8
head:ffffea0000bd7200 order:1 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea0001eebb88 ffffea0000bc9b88 ffff888017441b40
raw: ffff88802f5c9600 000000000010000b 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 6550, tgid 6546 (syz.5.679), ts 206240628291, free_ts 203890148009
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2532
 prep_new_page mm/page_alloc.c:2539 [inline]
 get_page_from_freelist+0x1a26/0x1ac0 mm/page_alloc.c:4328
 __alloc_pages+0x1df/0x4e0 mm/page_alloc.c:5614
 alloc_slab_page+0x5d/0x160 mm/slub.c:1799
 allocate_slab mm/slub.c:1944 [inline]
 new_slab+0x87/0x2c0 mm/slub.c:1997
 ___slab_alloc+0xbc6/0x1230 mm/slub.c:3154
 __slab_alloc mm/slub.c:3240 [inline]
 slab_alloc_node mm/slub.c:3325 [inline]
 __kmem_cache_alloc_node+0x1a0/0x260 mm/slub.c:3398
 __do_kmalloc_node mm/slab_common.c:935 [inline]
 __kmalloc+0xa0/0x240 mm/slab_common.c:949
 kmalloc include/linux/slab.h:568 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 new_dir fs/proc/proc_sysctl.c:973 [inline]
 get_subdir fs/proc/proc_sysctl.c:1017 [inline]
 __register_sysctl_table+0x96c/0xe70 fs/proc/proc_sysctl.c:1379
 __devinet_sysctl_register+0x253/0x320 net/ipv4/devinet.c:2612
 devinet_sysctl_register+0x17c/0x1f0 net/ipv4/devinet.c:2652
 inetdev_init+0x2b4/0x4f0 net/ipv4/devinet.c:280
 inetdev_event+0x270/0x1410 net/ipv4/devinet.c:1547
 notifier_call_chain kernel/notifier.c:87 [inline]
 raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:455
 call_netdevice_notifiers_extack net/core/dev.c:2039 [inline]
 call_netdevice_notifiers net/core/dev.c:2053 [inline]
 register_netdevice+0x1600/0x1aa0 net/core/dev.c:10237
 register_netdev+0x37/0x50 net/core/dev.c:10332
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1459 [inline]
 free_pcp_prepare mm/page_alloc.c:1509 [inline]
 free_unref_page_prepare+0x8b4/0x9a0 mm/page_alloc.c:3384
 free_unref_page+0x2e/0x3f0 mm/page_alloc.c:3479
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x76/0xe0 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x144/0x160 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x1e/0x80 mm/kasan/common.c:305
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x480 mm/slab.h:737
 slab_alloc_node mm/slub.c:3359 [inline]
 slab_alloc mm/slub.c:3367 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3374 [inline]
 kmem_cache_alloc+0x123/0x2f0 mm/slub.c:3383
 sk_prot_alloc+0x57/0x210 net/core/sock.c:2046
 sk_alloc+0x36/0x340 net/core/sock.c:2108
 inet_create+0x780/0x1020 net/ipv4/af_inet.c:319
 __sock_create+0x4a2/0x940 net/socket.c:1550
 sock_create net/socket.c:1606 [inline]
 __sys_socket_create net/socket.c:1643 [inline]
 __sys_socket+0xc4/0x190 net/socket.c:1671
 __do_sys_socket net/socket.c:1684 [inline]
 __se_sys_socket net/socket.c:1682 [inline]
 __x64_sys_socket+0x76/0x80 net/socket.c:1682
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
 ffff88802f5c9100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88802f5c9180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88802f5c9200: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff88802f5c9280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88802f5c9300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
   0:	d0 d7                	rcl    %bh
   2:	43 8c 48 89          	rex.XB mov %cs,-0x77(%r8)
   6:	de e8                	fsubrp %st,%st(0)
   8:	c8 be 3b 08          	enter  $0x3bbe,$0x8
   c:	31 ed                	xor    %ebp,%ebp
   e:	eb d7                	jmp    0xffffffe7
  10:	00 00                	add    %al,(%rax)
  12:	cc                   	int3
  13:	cc                   	int3
  14:	89 f6                	mov    %esi,%esi
  16:	48 8b 0c 24          	mov    (%rsp),%rcx
  1a:	31 d2                	xor    %edx,%edx
  1c:	e9 a3 ec ff ff       	jmp    0xffffecc4
  21:	0f 1f 00             	nopl   (%rax)
  24:	89 f6                	mov    %esi,%esi
  26:	48 8b 0c 24          	mov    (%rsp),%rcx
* 2a:	ba 01 00 00 00       	mov    $0x1,%edx <-- trapping instruction
  2f:	e9 90 ec ff ff       	jmp    0xffffecc4
  34:	55                   	push   %rbp
  35:	41 56                	push   %r14
  37:	53                   	push   %rbx
  38:	48 89 d3             	mov    %rdx,%rbx
  3b:	89 f5                	mov    %esi,%ebp
  3d:	49 89 fe             	mov    %rdi,%r14