==================================================================
BUG: KASAN: use-after-free in fib_flush+0x77/0x120 net/ipv4/fib_frontend.c:193
Read of size 8 at addr ffff8881134ae000 by task kworker/u4:6/3093
CPU: 0 PID: 3093 Comm: kworker/u4:6 Tainted: G W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2025
Workqueue: netns cleanup_net
Call Trace:
__dump_stack+0x21/0x24 lib/dump_stack.c:77
dump_stack_lvl+0x169/0x1d8 lib/dump_stack.c:118
print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:435 [inline]
kasan_report+0xe2/0x130 mm/kasan/report.c:452
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309
fib_flush+0x77/0x120 net/ipv4/fib_frontend.c:193
__remove_nexthop_fib+0xab/0x260 net/ipv4/nexthop.c:879
__remove_nexthop net/ipv4/nexthop.c:893 [inline]
remove_nexthop+0x75/0x4d0 net/ipv4/nexthop.c:919
remove_nh_grp_entry net/ipv4/nexthop.c:797 [inline]
remove_nexthop_from_groups+0x193/0xe40 net/ipv4/nexthop.c:846
__remove_nexthop net/ipv4/nexthop.c:904 [inline]
remove_nexthop+0x38a/0x4d0 net/ipv4/nexthop.c:919
flush_all_nexthops net/ipv4/nexthop.c:1237 [inline]
nexthop_net_exit+0x3a/0xa0 net/ipv4/nexthop.c:2012
ops_exit_list net/core/net_namespace.c:185 [inline]
cleanup_net+0x586/0xb70 net/core/net_namespace.c:609
process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301
worker_thread+0xa6a/0x13b0 kernel/workqueue.c:2447
kthread+0x346/0x3d0 kernel/kthread.c:313
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
Allocated by task 3449:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:45 [inline]
set_alloc_info mm/kasan/common.c:430 [inline]
____kasan_kmalloc mm/kasan/common.c:509 [inline]
__kasan_kmalloc+0xda/0x110 mm/kasan/common.c:518
kasan_kmalloc include/linux/kasan.h:254 [inline]
kmem_cache_alloc_trace+0x184/0x2e0 mm/slub.c:2979
kmalloc include/linux/slab.h:552 [inline]
kzalloc include/linux/slab.h:664 [inline]
ip_fib_net_init net/ipv4/fib_frontend.c:1547 [inline]
fib_net_init+0xe0/0x2c0 net/ipv4/fib_frontend.c:1606
ops_init+0x1ba/0x4a0 net/core/net_namespace.c:144
setup_net+0x36d/0xb50 net/core/net_namespace.c:345
copy_net_ns+0x314/0x520 net/core/net_namespace.c:486
create_new_namespaces+0x3a2/0x650 kernel/nsproxy.c:110
unshare_nsproxy_namespaces+0x120/0x170 kernel/nsproxy.c:231
ksys_unshare+0x4ac/0x7d0 kernel/fork.c:3156
__do_sys_unshare kernel/fork.c:3224 [inline]
__se_sys_unshare kernel/fork.c:3222 [inline]
__x64_sys_unshare+0x38/0x40 kernel/fork.c:3222
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb
Freed by task 3093:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362
__kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
kasan_slab_free include/linux/kasan.h:220 [inline]
slab_free_hook mm/slub.c:1600 [inline]
slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
slab_free mm/slub.c:3208 [inline]
kfree+0xc0/0x270 mm/slub.c:4196
ip_fib_net_exit+0x32f/0x350 net/ipv4/fib_frontend.c:1595
fib_net_exit+0x6c/0x80 net/ipv4/fib_frontend.c:1629
ops_exit_list net/core/net_namespace.c:185 [inline]
cleanup_net+0x586/0xb70 net/core/net_namespace.c:609
process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301
worker_thread+0xa6a/0x13b0 kernel/workqueue.c:2447
kthread+0x346/0x3d0 kernel/kthread.c:313
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
Last potentially related work creation:
kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
__kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
kvfree_call_rcu+0x10c/0x620 kernel/rcu/tree.c:3539
drop_sysctl_table+0x2ef/0x410 fs/proc/proc_sysctl.c:1684
unregister_sysctl_table+0x75/0x120 fs/proc/proc_sysctl.c:1722
unregister_net_sysctl_table+0x15/0x20 net/sysctl_net.c:127
__devinet_sysctl_unregister net/ipv4/devinet.c:2621 [inline]
devinet_sysctl_unregister net/ipv4/devinet.c:2649 [inline]
inetdev_destroy net/ipv4/devinet.c:326 [inline]
inetdev_event+0x79d/0x1030 net/ipv4/devinet.c:1612
notifier_call_chain kernel/notifier.c:83 [inline]
raw_notifier_call_chain+0x90/0x100 kernel/notifier.c:410
call_netdevice_notifiers_info net/core/dev.c:2054 [inline]
call_netdevice_notifiers_extack net/core/dev.c:2066 [inline]
call_netdevice_notifiers net/core/dev.c:2080 [inline]
unregister_netdevice_many+0xf8b/0x1980 net/core/dev.c:10767
default_device_exit_batch+0x330/0x390 net/core/dev.c:11287
ops_exit_list net/core/net_namespace.c:190 [inline]
cleanup_net+0x5fb/0xb70 net/core/net_namespace.c:609
process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301
worker_thread+0xa6a/0x13b0 kernel/workqueue.c:2447
kthread+0x346/0x3d0 kernel/kthread.c:313
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
Second to last potentially related work creation:
kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
__kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
__call_rcu kernel/rcu/tree.c:2980 [inline]
call_rcu+0x10e/0x1050 kernel/rcu/tree.c:3054
netlink_release+0x1288/0x1690 net/netlink/af_netlink.c:795
__sock_release net/socket.c:597 [inline]
sock_close+0xe0/0x270 net/socket.c:1286
__fput+0x2fb/0x770 fs/file_table.c:281
____fput+0x15/0x20 fs/file_table.c:314
task_work_run+0x127/0x190 kernel/task_work.c:189
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:172
exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199
syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274
do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56
entry_SYSCALL_64_after_hwframe+0x61/0xcb
The buggy address belongs to the object at ffff8881134ae000
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 0 bytes inside of
2048-byte region [ffff8881134ae000, ffff8881134ae800)
The buggy address belongs to the page:
page:ffffea00044d2a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1134a8
head:ffffea00044d2a00 order:3 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 0000000000000000 0000000100000001 ffff888100042d80
raw: 0000000000000000 0000000000080008 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x1d2a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 411, ts 32321109713, free_ts 32315617816
set_page_owner include/linux/page_owner.h:35 [inline]
post_alloc_hook mm/page_alloc.c:2456 [inline]
prep_new_page+0x179/0x180 mm/page_alloc.c:2462
get_page_from_freelist+0x2235/0x23d0 mm/page_alloc.c:4254
__alloc_pages_nodemask+0x268/0x5f0 mm/page_alloc.c:5370
alloc_slab_page mm/slub.c:-1 [inline]
allocate_slab mm/slub.c:1813 [inline]
new_slab+0x84/0x3f0 mm/slub.c:1874
new_slab_objects mm/slub.c:2632 [inline]
___slab_alloc+0x2a6/0x450 mm/slub.c:2796
__slab_alloc+0x63/0xa0 mm/slub.c:2836
slab_alloc_node mm/slub.c:2918 [inline]
slab_alloc mm/slub.c:2960 [inline]
__kmalloc_track_caller+0x1ef/0x320 mm/slub.c:4541
__kmalloc_reserve net/core/skbuff.c:144 [inline]
__alloc_skb+0xdc/0x520 net/core/skbuff.c:212
alloc_skb include/linux/skbuff.h:1126 [inline]
nlmsg_new include/net/netlink.h:953 [inline]
audit_buffer_alloc kernel/audit.c:1799 [inline]
audit_log_start+0x3df/0x860 kernel/audit.c:1917
common_lsm_audit+0xd3/0x17f0 security/lsm_audit.c:457
slow_avc_audit+0x1ac/0x220 security/selinux/avc.c:798
avc_audit security/selinux/include/avc.h:140 [inline]
avc_has_perm+0x1ca/0x360 security/selinux/avc.c:1201
inode_has_perm security/selinux/hooks.c:1657 [inline]
file_path_has_perm security/selinux/hooks.c:1702 [inline]
selinux_file_open+0x467/0x620 security/selinux/hooks.c:3979
security_file_open+0x62/0xa0 security/security.c:1582
do_dentry_open+0x39b/0x1090 fs/open.c:806
vfs_open+0x73/0x80 fs/open.c:942
page last free stack trace:
reset_page_owner include/linux/page_owner.h:28 [inline]
free_pages_prepare mm/page_alloc.c:1349 [inline]
__free_pages_ok+0x7fc/0x820 mm/page_alloc.c:1629
free_the_page mm/page_alloc.c:5431 [inline]
__free_pages+0xdd/0x380 mm/page_alloc.c:5440
__free_slab+0xcf/0x190 mm/slub.c:1899
free_slab mm/slub.c:1914 [inline]
discard_slab+0x29/0x40 mm/slub.c:1920
__slab_free+0x313/0x3a0 mm/slub.c:3136
do_slab_free mm/slub.c:3196 [inline]
___cache_free+0x111/0x130 mm/slub.c:3215
qlink_free+0x50/0x90 mm/kasan/quarantine.c:157
qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176
kasan_quarantine_reduce+0x14a/0x160 mm/kasan/quarantine.c:283
__kasan_slab_alloc+0x2f/0xf0 mm/kasan/common.c:440
kasan_slab_alloc include/linux/kasan.h:244 [inline]
slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580
slab_alloc_node mm/slub.c:2952 [inline]
slab_alloc mm/slub.c:2960 [inline]
kmem_cache_alloc+0x165/0x2e0 mm/slub.c:2965
getname_flags+0xb9/0x500 fs/namei.c:141
getname+0x19/0x20 fs/namei.c:212
do_sys_openat2+0xd9/0x6d0 fs/open.c:1211
do_sys_open fs/open.c:1233 [inline]
__do_sys_openat fs/open.c:1249 [inline]
__se_sys_openat fs/open.c:1244 [inline]
__x64_sys_openat+0x136/0x160 fs/open.c:1244
Memory state around the buggy address:
ffff8881134adf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881134adf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8881134ae000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881134ae080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881134ae100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
general protection fault, probably for non-canonical address 0xfd90650a6a882aa8: 0000 [#1] PREEMPT SMP KASAN
KASAN: maybe wild-memory-access in range [0xec83485354415540-0xec83485354415547]
CPU: 1 PID: 3093 Comm: kworker/u4:6 Tainted: G B W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2025
Workqueue: netns cleanup_net
RIP: 0010:fib_table_flush+0x31a/0x1330 net/ipv4/fib_trie.c:1992
Code: 38 c1 0f 8c 71 ff ff ff 48 89 df e8 70 10 bf fd e9 64 ff ff ff 4c 89 6c 24 38 48 89 44 24 20 48 8d 58 05 48 89 d8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 99 0d 00 00 0f b6 1b 31 ff 89 de e8 dd
RSP: 0018:ffffc90000b37840 EFLAGS: 00010a03
RAX: 1d90690a6a882aa8 RBX: ec83485354415546 RCX: ffff88811e37cf00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90000b379c0 R08: 0000000000000004 R09: 0000000000000003
R10: fffffbfff0d8ee48 R11: 1ffffffff0d8ee48 R12: dffffc0000000000
R13: 0000000000000001 R14: ffffffff83d9b840 R15: ffff8881180a4000
FS: 0000000000000000(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000003 CR3: 000000010c2fe000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
fib_flush+0xb5/0x120 net/ipv4/fib_frontend.c:194
__remove_nexthop_fib+0xab/0x260 net/ipv4/nexthop.c:879
__remove_nexthop net/ipv4/nexthop.c:893 [inline]
remove_nexthop+0x75/0x4d0 net/ipv4/nexthop.c:919
remove_nh_grp_entry net/ipv4/nexthop.c:797 [inline]
remove_nexthop_from_groups+0x193/0xe40 net/ipv4/nexthop.c:846
__remove_nexthop net/ipv4/nexthop.c:904 [inline]
remove_nexthop+0x38a/0x4d0 net/ipv4/nexthop.c:919
flush_all_nexthops net/ipv4/nexthop.c:1237 [inline]
nexthop_net_exit+0x3a/0xa0 net/ipv4/nexthop.c:2012
ops_exit_list net/core/net_namespace.c:185 [inline]
cleanup_net+0x586/0xb70 net/core/net_namespace.c:609
process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301
worker_thread+0xa6a/0x13b0 kernel/workqueue.c:2447
kthread+0x346/0x3d0 kernel/kthread.c:313
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
Modules linked in:
---[ end trace 06ac0d76b25e81df ]---
RIP: 0010:fib_table_flush+0x31a/0x1330 net/ipv4/fib_trie.c:1992
Code: 38 c1 0f 8c 71 ff ff ff 48 89 df e8 70 10 bf fd e9 64 ff ff ff 4c 89 6c 24 38 48 89 44 24 20 48 8d 58 05 48 89 d8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 99 0d 00 00 0f b6 1b 31 ff 89 de e8 dd
RSP: 0018:ffffc90000b37840 EFLAGS: 00010a03
RAX: 1d90690a6a882aa8 RBX: ec83485354415546 RCX: ffff88811e37cf00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90000b379c0 R08: 0000000000000004 R09: 0000000000000003
R10: fffffbfff0d8ee48 R11: 1ffffffff0d8ee48 R12: dffffc0000000000
R13: 0000000000000001 R14: ffffffff83d9b840 R15: ffff8881180a4000
FS: 0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000010d069000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 38 c1 cmp %al,%cl
2: 0f 8c 71 ff ff ff jl 0xffffff79
8: 48 89 df mov %rbx,%rdi
b: e8 70 10 bf fd call 0xfdbf1080
10: e9 64 ff ff ff jmp 0xffffff79
15: 4c 89 6c 24 38 mov %r13,0x38(%rsp)
1a: 48 89 44 24 20 mov %rax,0x20(%rsp)
1f: 48 8d 58 05 lea 0x5(%rax),%rbx
23: 48 89 d8 mov %rbx,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 0f b6 04 20 movzbl (%rax,%r12,1),%eax <-- trapping instruction
2f: 84 c0 test %al,%al
31: 0f 85 99 0d 00 00 jne 0xdd0
37: 0f b6 1b movzbl (%rbx),%ebx
3a: 31 ff xor %edi,%edi
3c: 89 de mov %ebx,%esi
3e: e8 .byte 0xe8
3f: dd .byte 0xdd