==================================================================
BUG: KASAN: slab-use-after-free in ax25_heartbeat_expiry+0x115/0x140 net/ax25/ax25_timer.c:127
Read of size 4 at addr ffff88803f886660 by task dhcpcd-run-hook/21795
CPU: 0 UID: 0 PID: 21795 Comm: dhcpcd-run-hook Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xba/0x230 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
ax25_heartbeat_expiry+0x115/0x140 net/ax25/ax25_timer.c:127
call_timer_fn+0x192/0x640 kernel/time/timer.c:1748
expire_timers kernel/time/timer.c:1799 [inline]
__run_timers kernel/time/timer.c:2373 [inline]
__run_timer_base+0x652/0x8b0 kernel/time/timer.c:2385
run_timer_base kernel/time/timer.c:2394 [inline]
run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2404
handle_softirqs+0x22a/0x870 kernel/softirq.c:622
__do_softirq kernel/softirq.c:656 [inline]
invoke_softirq kernel/softirq.c:496 [inline]
__irq_exit_rcu+0x5f/0x150 kernel/softirq.c:723
irq_exit_rcu+0x9/0x30 kernel/softirq.c:739
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1056
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:rcu_is_watching_curr_cpu include/linux/context_tracking.h:128 [inline]
RIP: 0010:rcu_is_watching+0x2e/0xb0 kernel/rcu/tree.c:752
Code: 41 57 41 56 53 65 ff 05 a0 fa 70 11 e8 0b 87 02 0a 89 c3 83 f8 08 73 65 49 bf 00 00 00 00 00 fc ff df 4c 8d 34 dd 90 97 1a 8e <4c> 89 f0 48 c1 e8 03 42 80 3c 38 00 74 08 4c 89 f7 e8 bc 0f 85 00
RSP: 0018:ffffc9000d7bf330 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000080000001
RDX: ffff88807a855ac0 RSI: ffffffff8c27a460 RDI: ffffffff8c27a420
RBP: 0000000000000001 R08: ffffffff81d53046 R09: ffffffff8e7602e0
R10: ffffc9000d7bf438 R11: ffffffff81b0b130 R12: 0000000000002c3e
R13: dffffc0000000000 R14: ffffffff8e1a9790 R15: dffffc0000000000
rcu_read_unlock include/linux/rcupdate.h:879 [inline]
is_bpf_text_address+0x207/0x2b0 kernel/bpf/core.c:750
kernel_text_address+0xa5/0xe0 kernel/extable.c:125
__kernel_text_address+0xd/0x30 kernel/extable.c:79
unwind_get_return_address+0x4d/0x90 arch/x86/kernel/unwind_orc.c:385
arch_stack_walk+0xfb/0x150 arch/x86/kernel/stacktrace.c:26
stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__kmalloc_cache_noprof+0x31c/0x660 mm/slub.c:5339
kmalloc_noprof include/linux/slab.h:962 [inline]
single_open+0x5a/0x240 fs/seq_file.c:576
proc_reg_open+0x247/0x540 fs/proc/inode.c:511
do_dentry_open+0x785/0x14e0 fs/open.c:949
vfs_open+0x3b/0x340 fs/open.c:1081
do_open fs/namei.c:4671 [inline]
path_openat+0x2e08/0x3860 fs/namei.c:4830
do_file_open+0x23e/0x4a0 fs/namei.c:4859
do_sys_openat2+0x113/0x200 fs/open.c:1366
do_sys_open fs/open.c:1372 [inline]
__do_sys_openat fs/open.c:1388 [inline]
__se_sys_openat fs/open.c:1383 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4d165f6407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffc90de8d10 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f4d164a6c80 RCX: 00007f4d165f6407
RDX: 0000000000080000 RSI: 00007f4d1653b2e2 RDI: ffffffffffffff9c
RBP: 0000000000000008 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 00007f4d1653b3ae
R13: 00007f4d1653b3ae R14: 0000000000000001 R15: 0000000000000000
Allocated by task 18939:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__kmalloc_cache_noprof+0x31c/0x660 mm/slub.c:5339
kmalloc_noprof include/linux/slab.h:962 [inline]
kzalloc_noprof include/linux/slab.h:1204 [inline]
ax25_dev_device_up+0x54/0x5f0 net/ax25/ax25_dev.c:57
ax25_device_event+0x127/0x8a0 net/ax25/af_ax25.c:143
notifier_call_chain+0x1be/0x400 kernel/notifier.c:85
call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
call_netdevice_notifiers net/core/dev.c:2301 [inline]
__dev_notify_flags+0x1a9/0x310 net/core/dev.c:9792
netif_change_flags+0xe8/0x1a0 net/core/dev.c:9821
dev_change_flags+0x130/0x260 net/core/dev_api.c:68
dev_ioctl+0x7b4/0x1150 net/core/dev_ioctl.c:814
sock_do_ioctl+0x23e/0x320 net/socket.c:1268
sock_ioctl+0x5c6/0x7f0 net/socket.c:1375
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 15:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2687 [inline]
__rcu_free_sheaf_prepare+0x129/0x290 mm/slub.c:2917
rcu_free_sheaf+0x31/0x200 mm/slub.c:5770
rcu_do_batch kernel/rcu/tree.c:2617 [inline]
rcu_core+0x7cd/0x1070 kernel/rcu/tree.c:2869
handle_softirqs+0x22a/0x870 kernel/softirq.c:622
run_ksoftirqd+0x36/0x60 kernel/softirq.c:1063
smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160
kthread+0x388/0x470 kernel/kthread.c:467
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
The buggy address belongs to the object at ffff88803f886600
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 96 bytes inside of
freed 256-byte region [ffff88803f886600, ffff88803f886700)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88803f887200 pfn:0x3f886
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000240(workingset|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000240 ffff88813fea8b40 ffffea00016f9910 ffffea000120d610
raw: ffff88803f887200 000000000010000c 00000000f5000000 0000000000000000
head: 00fff00000000240 ffff88813fea8b40 ffffea00016f9910 ffffea000120d610
head: ffff88803f887200 000000000010000c 00000000f5000000 0000000000000000
head: 00fff00000000001 ffffea0000fe2181 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0x52820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 31659, tgid 31658 (syz.1.7815), ts 926608537265, free_ts 758919470692
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889
prep_new_page mm/page_alloc.c:1897 [inline]
get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3962
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250
alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2485
alloc_slab_page mm/slub.c:3253 [inline]
allocate_slab+0x83/0x660 mm/slub.c:3444
new_slab mm/slub.c:3502 [inline]
___slab_alloc+0x150/0x6b0 mm/slub.c:4376
__slab_alloc_node mm/slub.c:4442 [inline]
slab_alloc_node mm/slub.c:4818 [inline]
__do_kmalloc_node mm/slub.c:5218 [inline]
__kmalloc_noprof+0x18a/0x760 mm/slub.c:5231
kmalloc_noprof include/linux/slab.h:966 [inline]
kzalloc_noprof include/linux/slab.h:1204 [inline]
hash_ip4_resize+0xa70/0x1a20 net/netfilter/ipset/ip_set_hash_gen.h:725
call_ad+0x463/0xb60 net/netfilter/ipset/ip_set_core.c:1757
ip_set_ad+0x824/0x9d0 net/netfilter/ipset/ip_set_core.c:1841
nfnetlink_rcv_msg+0xc00/0x12c0 net/netfilter/nfnetlink.c:302
netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550
nfnetlink_rcv+0x2c0/0x27b0 net/netfilter/nfnetlink.c:669
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg net/socket.c:742 [inline]
____sys_sendmsg+0xa68/0xad0 net/socket.c:2592
page last free pid 13377 tgid 13377 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1433 [inline]
__free_frozen_pages+0xc2b/0xdb0 mm/page_alloc.c:2978
kasan_depopulate_vmalloc_pte+0x6d/0x90 mm/kasan/shadow.c:484
apply_to_pte_range mm/memory.c:3243 [inline]
apply_to_pmd_range mm/memory.c:3287 [inline]
apply_to_pud_range mm/memory.c:3323 [inline]
apply_to_p4d_range mm/memory.c:3359 [inline]
__apply_to_page_range+0xbdc/0x1420 mm/memory.c:3395
__kasan_release_vmalloc+0xa2/0xd0 mm/kasan/shadow.c:602
kasan_release_vmalloc include/linux/kasan.h:593 [inline]
kasan_release_vmalloc_node mm/vmalloc.c:2290 [inline]
purge_vmap_node+0x220/0x960 mm/vmalloc.c:2312
__purge_vmap_area_lazy+0x779/0xb70 mm/vmalloc.c:2402
drain_vmap_area_work+0x27/0x40 mm/vmalloc.c:2436
process_one_work kernel/workqueue.c:3275 [inline]
process_scheduled_works+0xb02/0x1830 kernel/workqueue.c:3358
worker_thread+0xa50/0xfc0 kernel/workqueue.c:3439
kthread+0x388/0x470 kernel/kthread.c:467
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
Memory state around the buggy address:
ffff88803f886500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88803f886580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88803f886600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88803f886680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88803f886700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 41 57 push %r15
2: 41 56 push %r14
4: 53 push %rbx
5: 65 ff 05 a0 fa 70 11 incl %gs:0x1170faa0(%rip) # 0x1170faac
c: e8 0b 87 02 0a call 0xa02871c
11: 89 c3 mov %eax,%ebx
13: 83 f8 08 cmp $0x8,%eax
16: 73 65 jae 0x7d
18: 49 bf 00 00 00 00 00 movabs $0xdffffc0000000000,%r15
1f: fc ff df
22: 4c 8d 34 dd 90 97 1a lea -0x71e56870(,%rbx,8),%r14
29: 8e
* 2a: 4c 89 f0 mov %r14,%rax <-- trapping instruction
2d: 48 c1 e8 03 shr $0x3,%rax
31: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1)
36: 74 08 je 0x40
38: 4c 89 f7 mov %r14,%rdi
3b: e8 bc 0f 85 00 call 0x850ffc