================================================================== 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