==================================================================
BUG: KASAN: use-after-free in ax25_heartbeat_expiry+0x10c/0x130 net/ax25/ax25_timer.c:125
Read of size 4 at addr ffff888143fa8f50 by task syz.0.124/4615
CPU: 1 PID: 4615 Comm: syz.0.124 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
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
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:lock_release+0x5a4/0x8a0 kernel/locking/lockdep.c:5647
Code: 80 00 00 00 f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 2c 04 f8 75 6f 41 f7 c7 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 2c 00 00 00 00 43 c7 44 2c 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc900056f6b40 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 1672b6fb0ac2f54d RCX: 0c1a617d2d132800
RDX: 0000000000000002 RSI: ffffffff8a2b3a20 RDI: ffffffff8a79f980
RBP: ffffc900056f6c50 R08: ffffffff8d89e36f R09: 1ffffffff1b13c6d
R10: dffffc0000000000 R11: fffffbfff1b13c6e R12: 1ffff92000aded74
R13: dffffc0000000000 R14: ffff888021a0a8a0 R15: 0000000000000246
percpu_ref_get include/linux/percpu-refcount.h:222 [inline]
css_get include/linux/cgroup.h:325 [inline]
charge_memcg+0x13d/0x2f0 mm/memcontrol.c:6769
__mem_cgroup_charge+0x21/0x80 mm/memcontrol.c:6801
mem_cgroup_charge include/linux/memcontrol.h:700 [inline]
shmem_add_to_page_cache+0xa98/0x14d0 mm/shmem.c:718
shmem_getpage_gfp+0x1796/0x2d40 mm/shmem.c:1940
shmem_getpage mm/shmem.c:151 [inline]
shmem_write_begin+0xcd/0x1a0 mm/shmem.c:2474
generic_perform_write+0x2b6/0x550 mm/filemap.c:3785
__generic_file_write_iter+0x25f/0x4e0 mm/filemap.c:3912
generic_file_write_iter+0xa6/0x1b0 mm/filemap.c:3944
__kernel_write+0x51c/0x970 fs/read_write.c:539
__dump_emit+0x249/0x370 fs/coredump.c:943
dump_user_range+0x84/0x340 fs/coredump.c:1017
elf_core_dump+0x2fbd/0x3500 fs/binfmt_elf.c:2285
do_coredump+0x14c7/0x2ac0 fs/coredump.c:894
get_signal+0x40a/0x12c0 kernel/signal.c:2886
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
irqentry_exit_to_user_mode+0x5/0x30 kernel/entry/common.c:320
exc_page_fault+0x88/0x100 arch/x86/mm/fault.c:1499
asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
RIP: 0033:0x7f8f84b717a1
Code: 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 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f
RSP: 002b:fffffffffffffe70 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 00007f8f84deb090 RCX: 00007f8f84b71799
RDX: 0000000000000000 RSI: fffffffffffffe70 RDI: 0000000000008000
RBP: 00007f8f84c07bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f8f84deb128 R14: 00007f8f84deb090 R15: 00007ffe5fe4d618
Allocated by task 4552:
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 4623:
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 ffff888143fa8f00
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 80 bytes inside of
192-byte region [ffff888143fa8f00, ffff888143fa8fc0)
The buggy address belongs to the page:
page:ffffea00050fea00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x143fa8
flags: 0x57ff00000000200(slab|node=1|zone=2|lastcpupid=0x7ff)
raw: 057ff00000000200 0000000000000000 0000000100000001 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 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 1, ts 2502252186, free_ts 0
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_page_interleave+0x24/0x1e0 mm/mempolicy.c:2031
alloc_slab_page mm/slub.c:1780 [inline]
allocate_slab mm/slub.c:1917 [inline]
new_slab+0xc0/0x4b0 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]
__kmalloc_track_caller+0x1cb/0x330 mm/slub.c:4930
__do_krealloc mm/slab_common.c:1244 [inline]
krealloc+0x5a/0xf0 mm/slab_common.c:1277
add_sysfs_param+0xe8/0x930 kernel/params.c:651
kernel_add_sysfs_param+0xaf/0x120 kernel/params.c:812
param_sysfs_builtin+0x183/0x200 kernel/params.c:851
param_sysfs_init+0x66/0x70 kernel/params.c:972
do_one_initcall+0x272/0x730 init/main.c:1316
do_initcall_level+0x137/0x1f0 init/main.c:1389
do_initcalls+0x4b/0x90 init/main.c:1405
kernel_init_freeable+0x3e9/0x570 init/main.c:1629
kernel_init+0x19/0x1b0 init/main.c:1520
page_owner free stack trace missing
Memory state around the buggy address:
ffff888143fa8e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888143fa8e80: 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888143fa8f00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888143fa8f80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff888143fa9000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================
----------------
Code disassembly (best guess):
0: 80 00 00 addb $0x0,(%rax)
3: 00 f7 add %dh,%bh
5: 84 24 80 test %ah,(%rax,%rax,4)
8: 00 00 add %al,(%rax)
a: 00 00 add %al,(%rax)
c: 02 00 add (%rax),%al
e: 00 43 c6 add %al,-0x3a(%rbx)
11: 44 2c 04 rex.R sub $0x4,%al
14: f8 clc
15: 75 6f jne 0x86
17: 41 f7 c7 00 02 00 00 test $0x200,%r15d
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 04 2c 00 00 00 movq $0x0,(%r12,%r13,1) <-- trapping instruction
31: 00
32: 43 c7 44 2c 08 00 00 movl $0x0,0x8(%r12,%r13,1)
39: 00 00
3b: 65 gs
3c: 48 rex.W
3d: 8b .byte 0x8b
3e: 04 25 add $0x25,%al