[v5.15] KASAN: use-after-free Read in ax25_unregister_dev_sysctl (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7b232985052f Linux 5.15.199
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11438ae6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=0e0f9d0f44057b7c852f
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/97a23052e207/disk-7b232985.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e9871fb1bda3/vmlinux-7b232985.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b08e48f5be44/bzImage-7b232985.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0e0f9d...@syzkaller.appspotmail.com

device bond0 entered promiscuous mode
==================================================================
BUG: KASAN: use-after-free in ax25_unregister_dev_sysctl+0x33/0xa0 net/ax25/sysctl_net_ax25.c:172
Read of size 8 at addr ffff8880236da918 by task syz.2.441/5621

CPU: 1 PID: 5621 Comm: syz.2.441 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
Call Trace:
<TASK>
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_unregister_dev_sysctl+0x33/0xa0 net/ax25/sysctl_net_ax25.c:172
ax25_dev_device_down+0x5b/0x520 net/ax25/ax25_dev.c:101
ax25_device_event+0x4b4/0x4f0 net/ax25/af_ax25.c:144
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_close_many+0x29f/0x400 net/core/dev.c:1663
dev_close+0x154/0x210 net/core/dev.c:1685
bpq_device_event+0x2f4/0x9c0 drivers/net/hamradio/bpqether.c:548
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+0x158/0x300 net/core/dev.c:8906
dev_change_flags+0xe3/0x1a0 net/core/dev.c:8942
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
RIP: 0033:0x7fd04608ff79
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:00007fd0442ea028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fd046309fa0 RCX: 00007fd04608ff79
RDX: 0000200000000100 RSI: 0000000000008914 RDI: 0000000000000004
RBP: 00007fd0461267e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd04630a038 R14: 00007fd046309fa0 R15: 00007ffeca66dcd8
</TASK>

Allocated by task 4404:
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:8904
dev_change_flags+0xe3/0x1a0 net/core/dev.c:8942
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 5420:
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
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
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

Last potentially related work creation:
kasan_save_stack+0x35/0x60 mm/kasan/common.c:38
kasan_record_aux_stack+0xb8/0x100 mm/kasan/generic.c:348
insert_work+0x54/0x3d0 kernel/workqueue.c:1366
__queue_work+0x9c5/0xd50 kernel/workqueue.c:1532
queue_work_on+0x124/0x1f0 kernel/workqueue.c:1559
queue_work include/linux/workqueue.h:512 [inline]
netdevice_queue_work drivers/infiniband/core/roce_gid_mgmt.c:659 [inline]
netdevice_event+0x803/0x900 drivers/infiniband/core/roce_gid_mgmt.c:802
notifier_call_chain kernel/notifier.c:83 [inline]
raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:391
__netdev_upper_dev_link+0x41e/0x590 net/core/dev.c:8212
netdev_upper_dev_link+0xad/0xf0 net/core/dev.c:8253
register_vlan_dev+0x3bd/0x810 net/8021q/vlan.c:184
vlan_newlink+0x44c/0x610 net/8021q/vlan_netlink.c:195
__rtnl_newlink net/core/rtnetlink.c:3526 [inline]
rtnl_newlink+0x1359/0x1a50 net/core/rtnetlink.c:3574
rtnetlink_rcv_msg+0x844/0xf30 net/core/rtnetlink.c:5684
netlink_rcv_skb+0x1f5/0x440 net/netlink/af_netlink.c:2507
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x774/0x920 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:706 [inline]
__sock_sendmsg net/socket.c:718 [inline]
__sys_sendto+0x46d/0x620 net/socket.c:2072
__do_sys_sendto net/socket.c:2084 [inline]
__se_sys_sendto net/socket.c:2080 [inline]
__x64_sys_sendto+0xda/0xf0 net/socket.c:2080
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

Second to last potentially related work creation:
kasan_save_stack+0x35/0x60 mm/kasan/common.c:38
kasan_record_aux_stack+0xb8/0x100 mm/kasan/generic.c:348
insert_work+0x54/0x3d0 kernel/workqueue.c:1366
__queue_work+0x9c5/0xd50 kernel/workqueue.c:1532
queue_work_on+0x124/0x1f0 kernel/workqueue.c:1559
queue_work include/linux/workqueue.h:512 [inline]
call_usermodehelper_exec+0x2e3/0x520 kernel/umh.c:435
kobject_uevent_env+0x681/0x890 lib/kobject_uevent.c:633
driver_register+0x3e2/0x430 drivers/base/driver.c:248
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
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

The buggy address belongs to the object at ffff8880236da900
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 24 bytes inside of
192-byte region [ffff8880236da900, ffff8880236da9c0)
The buggy address belongs to the page:
page:ffffea00008db680 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8880236da300 pfn:0x236da
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 ffffea00008d9480 0000000200000002 ffff888016c41a00
raw: ffff8880236da300 000000008010000f 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 15154942718, 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:5487
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]
kmem_cache_alloc_trace+0x1a5/0x2a0 mm/slub.c:3250
kmalloc include/linux/slab.h:607 [inline]
kzalloc include/linux/slab.h:738 [inline]
call_usermodehelper_setup+0x8a/0x260 kernel/umh.c:365
kobject_uevent_env+0x65e/0x890 lib/kobject_uevent.c:629
kset_register+0x188/0x1f0 lib/kobject.c:894
bus_register+0x21c/0x6c0 drivers/base/bus.c:808
nsim_bus_init+0x13/0x70 drivers/net/netdevsim/bus.c:470
nsim_module_init+0x27/0x80 drivers/net/netdevsim/netdev.c:414
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
page_owner free stack trace missing

Memory state around the buggy address:
ffff8880236da800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8880236da880: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880236da900: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880236da980: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff8880236daa00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


---
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