==================================================================
BUG: KASAN: slab-use-after-free in decode_session6 net/xfrm/xfrm_policy.c:3494 [inline]
BUG: KASAN: slab-use-after-free in __xfrm_decode_session+0x18d7/0x20a0 net/xfrm/xfrm_policy.c:3600
Read of size 1 at addr ffff8880768055e4 by task syz.0.484/7340

CPU: 1 PID: 7340 Comm: syz.0.484 Not tainted 6.6.95-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xac/0x230 mm/kasan/report.c:475
 kasan_report+0x117/0x150 mm/kasan/report.c:588
 decode_session6 net/xfrm/xfrm_policy.c:3494 [inline]
 __xfrm_decode_session+0x18d7/0x20a0 net/xfrm/xfrm_policy.c:3600
 xfrm_decode_session_reverse include/net/xfrm.h:1243 [inline]
 icmpv6_route_lookup+0x358/0x590 net/ipv6/icmp.c:392
 icmp6_send+0x106a/0x1990 net/ipv6/icmp.c:604
 __icmpv6_send include/linux/icmpv6.h:28 [inline]
 icmpv6_send include/linux/icmpv6.h:49 [inline]
 ip6_link_failure+0x3b/0x4c0 net/ipv6/route.c:2825
 dst_link_failure include/net/dst.h:437 [inline]
 ip6_tnl_xmit+0xdf7/0x2a30 net/ipv6/ip6_tunnel.c:1283
 ipxip6_tnl_xmit net/ipv6/ip6_tunnel.c:1399 [inline]
 ip6_tnl_start_xmit+0xc10/0x1140 net/ipv6/ip6_tunnel.c:1447
 __netdev_start_xmit include/linux/netdevice.h:4943 [inline]
 netdev_start_xmit include/linux/netdevice.h:4957 [inline]
 xmit_one net/core/dev.c:3607 [inline]
 dev_hard_start_xmit+0x246/0x740 net/core/dev.c:3623
 sch_direct_xmit+0x252/0x4a0 net/sched/sch_generic.c:342
 qdisc_restart net/sched/sch_generic.c:407 [inline]
 __qdisc_run+0xab2/0x1570 net/sched/sch_generic.c:415
 __dev_xmit_skb net/core/dev.c:3907 [inline]
 __dev_queue_xmit+0xf02/0x35a0 net/core/dev.c:4379
 neigh_output include/net/neighbour.h:542 [inline]
 ip6_finish_output2+0xe2e/0x1650 net/ipv6/ip6_output.c:141
 ip6_fragment+0x13c5/0x1f90 net/ipv6/ip6_output.c:1023
 __ip6_finish_output net/ipv6/ip6_output.c:206 [inline]
 ip6_finish_output+0x5b4/0xaf0 net/ipv6/ip6_output.c:219
 dst_output include/net/dst.h:467 [inline]
 NF_HOOK include/linux/netfilter.h:304 [inline]
 ip6_xmit+0x10a7/0x1830 net/ipv6/ip6_output.c:360
 sctp_v6_xmit+0x9e3/0x1230 net/sctp/ipv6.c:250
 sctp_packet_transmit+0x2488/0x2a30 net/sctp/output.c:653
 sctp_packet_singleton+0x234/0x330 net/sctp/outqueue.c:783
 sctp_outq_flush_ctrl net/sctp/outqueue.c:914 [inline]
 sctp_outq_flush+0x4f1/0x3100 net/sctp/outqueue.c:1212
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:-1 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1198 [inline]
 sctp_do_sm+0x52d6/0x59a0 net/sctp/sm_sideeffect.c:1169
 sctp_primitive_ASSOCIATE+0x95/0xc0 net/sctp/primitive.c:73
 __sctp_connect+0x92f/0xd20 net/sctp/socket.c:1234
 sctp_setsockopt+0x458/0x11e0 net/sctp/socket.c:4617
 do_sock_setsockopt+0x254/0x3e0 net/socket.c:2322
 __sys_setsockopt net/socket.c:2345 [inline]
 __do_sys_setsockopt net/socket.c:2354 [inline]
 __se_sys_setsockopt net/socket.c:2351 [inline]
 __x64_sys_setsockopt+0x1be/0x250 net/socket.c:2351
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f557878e929
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f55795bc038 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007f55789b5fa0 RCX: 00007f557878e929
RDX: 000000000000006b RSI: 0000000000000084 RDI: 0000000000000003
RBP: 00007f5578810b39 R08: 000000000000001c R09: 0000000000000000
R10: 0000200000000380 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f55789b5fa0 R15: 00007ffd703c3e38
 </TASK>

Allocated by task 7340:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:383
 kasan_kmalloc include/linux/kasan.h:198 [inline]
 __do_kmalloc_node mm/slab_common.c:1007 [inline]
 __kmalloc_node_track_caller+0xb2/0x230 mm/slab_common.c:1027
 kmalloc_reserve+0x117/0x260 net/core/skbuff.c:581
 __alloc_skb+0x138/0x2c0 net/core/skbuff.c:650
 alloc_skb include/linux/skbuff.h:1284 [inline]
 alloc_skb_with_frags+0xca/0x7c0 net/core/skbuff.c:6328
 sock_alloc_send_pskb+0x857/0x990 net/core/sock.c:2799
 sock_alloc_send_skb include/net/sock.h:1903 [inline]
 __ip6_append_data+0x2a32/0x3c70 net/ipv6/ip6_output.c:1722
 ip6_append_data+0x1c3/0x380 net/ipv6/ip6_output.c:1915
 icmp6_send+0x122b/0x1990 net/ipv6/icmp.c:624
 __icmpv6_send include/linux/icmpv6.h:28 [inline]
 icmpv6_send include/linux/icmpv6.h:49 [inline]
 ip6_link_failure+0x3b/0x4c0 net/ipv6/route.c:2825
 dst_link_failure include/net/dst.h:437 [inline]
 ip6_tnl_xmit+0xdf7/0x2a30 net/ipv6/ip6_tunnel.c:1283
 ipxip6_tnl_xmit net/ipv6/ip6_tunnel.c:1399 [inline]
 ip6_tnl_start_xmit+0xc10/0x1140 net/ipv6/ip6_tunnel.c:1447
 __netdev_start_xmit include/linux/netdevice.h:4943 [inline]
 netdev_start_xmit include/linux/netdevice.h:4957 [inline]
 xmit_one net/core/dev.c:3607 [inline]
 dev_hard_start_xmit+0x246/0x740 net/core/dev.c:3623
 sch_direct_xmit+0x252/0x4a0 net/sched/sch_generic.c:342
 qdisc_restart net/sched/sch_generic.c:407 [inline]
 __qdisc_run+0xab2/0x1570 net/sched/sch_generic.c:415
 __dev_xmit_skb net/core/dev.c:3907 [inline]
 __dev_queue_xmit+0xf02/0x35a0 net/core/dev.c:4379
 neigh_output include/net/neighbour.h:542 [inline]
 ip6_finish_output2+0xe2e/0x1650 net/ipv6/ip6_output.c:141
 ip6_fragment+0x13c5/0x1f90 net/ipv6/ip6_output.c:1023
 __ip6_finish_output net/ipv6/ip6_output.c:206 [inline]
 ip6_finish_output+0x5b4/0xaf0 net/ipv6/ip6_output.c:219
 dst_output include/net/dst.h:467 [inline]
 NF_HOOK include/linux/netfilter.h:304 [inline]
 ip6_xmit+0x10a7/0x1830 net/ipv6/ip6_output.c:360
 sctp_v6_xmit+0x9e3/0x1230 net/sctp/ipv6.c:250
 sctp_packet_transmit+0x2488/0x2a30 net/sctp/output.c:653
 sctp_packet_singleton+0x234/0x330 net/sctp/outqueue.c:783
 sctp_outq_flush_ctrl net/sctp/outqueue.c:914 [inline]
 sctp_outq_flush+0x4f1/0x3100 net/sctp/outqueue.c:1212
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:-1 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1198 [inline]
 sctp_do_sm+0x52d6/0x59a0 net/sctp/sm_sideeffect.c:1169
 sctp_primitive_ASSOCIATE+0x95/0xc0 net/sctp/primitive.c:73
 __sctp_connect+0x92f/0xd20 net/sctp/socket.c:1234
 sctp_setsockopt+0x458/0x11e0 net/sctp/socket.c:4617
 do_sock_setsockopt+0x254/0x3e0 net/socket.c:2322
 __sys_setsockopt net/socket.c:2345 [inline]
 __do_sys_setsockopt net/socket.c:2354 [inline]
 __se_sys_setsockopt net/socket.c:2351 [inline]
 __x64_sys_setsockopt+0x1be/0x250 net/socket.c:2351
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 7340:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1806 [inline]
 slab_free_freelist_hook+0x130/0x1b0 mm/slub.c:1832
 slab_free mm/slub.c:3816 [inline]
 __kmem_cache_free+0xba/0x1f0 mm/slub.c:3829
 skb_kfree_head net/core/skbuff.c:945 [inline]
 skb_free_head net/core/skbuff.c:957 [inline]
 skb_release_data+0x634/0x800 net/core/skbuff.c:987
 skb_release_all net/core/skbuff.c:1053 [inline]
 __kfree_skb net/core/skbuff.c:1067 [inline]
 kfree_skb_reason+0x10e/0x170 net/core/skbuff.c:1103
 icmpv6_rcv+0xff8/0x1c10 net/ipv6/icmp.c:-1
 ip6_protocol_deliver_rcu+0xb7a/0x13c0 net/ipv6/ip6_input.c:438
 ip6_input_finish+0x184/0x2c0 net/ipv6/ip6_input.c:483
 NF_HOOK+0x303/0x390 include/linux/netfilter.h:304
 NF_HOOK+0x303/0x390 include/linux/netfilter.h:304
 __netif_receive_skb_one_core net/core/dev.c:5596 [inline]
 __netif_receive_skb+0xcc/0x290 net/core/dev.c:5710
 process_backlog+0x380/0x6e0 net/core/dev.c:6038
 __napi_poll+0xc0/0x460 net/core/dev.c:6600
 napi_poll net/core/dev.c:6667 [inline]
 net_rx_action+0x5ea/0xbf0 net/core/dev.c:6803
 handle_softirqs+0x280/0x820 kernel/softirq.c:578
 do_softirq+0xed/0x180 kernel/softirq.c:479
 __local_bh_enable_ip+0x178/0x1c0 kernel/softirq.c:406
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 rcu_read_unlock_bh include/linux/rcupdate.h:856 [inline]
 __dev_queue_xmit+0x1449/0x35a0 net/core/dev.c:4440
 neigh_output include/net/neighbour.h:542 [inline]
 ip6_finish_output2+0xe2e/0x1650 net/ipv6/ip6_output.c:141
 ip6_fragment+0x13c5/0x1f90 net/ipv6/ip6_output.c:1023
 __ip6_finish_output net/ipv6/ip6_output.c:206 [inline]
 ip6_finish_output+0x5b4/0xaf0 net/ipv6/ip6_output.c:219
 dst_output include/net/dst.h:467 [inline]
 NF_HOOK include/linux/netfilter.h:304 [inline]
 ip6_xmit+0x10a7/0x1830 net/ipv6/ip6_output.c:360
 sctp_v6_xmit+0x9e3/0x1230 net/sctp/ipv6.c:250
 sctp_packet_transmit+0x2488/0x2a30 net/sctp/output.c:653
 sctp_packet_singleton+0x234/0x330 net/sctp/outqueue.c:783
 sctp_outq_flush_ctrl net/sctp/outqueue.c:914 [inline]
 sctp_outq_flush+0x4f1/0x3100 net/sctp/outqueue.c:1212
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:-1 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1198 [inline]
 sctp_do_sm+0x52d6/0x59a0 net/sctp/sm_sideeffect.c:1169
 sctp_primitive_ASSOCIATE+0x95/0xc0 net/sctp/primitive.c:73
 __sctp_connect+0x92f/0xd20 net/sctp/socket.c:1234
 sctp_setsockopt+0x458/0x11e0 net/sctp/socket.c:4617
 do_sock_setsockopt+0x254/0x3e0 net/socket.c:2322
 __sys_setsockopt net/socket.c:2345 [inline]
 __do_sys_setsockopt net/socket.c:2354 [inline]
 __se_sys_setsockopt net/socket.c:2351 [inline]
 __x64_sys_setsockopt+0x1be/0x250 net/socket.c:2351
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff888076805000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1508 bytes inside of
 freed 2048-byte region [ffff888076805000, ffff888076805800)

The buggy address belongs to the physical page:
page:ffffea0001da0000 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x76800
head:ffffea0001da0000 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888017842000 dead000000000100 dead000000000122
raw: 0000000000000000 0000000080080008 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 0x1d28c0(GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 42, tgid 42 (kworker/u4:2), ts 98322237495, free_ts 98296257827
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
 prep_new_page mm/page_alloc.c:1561 [inline]
 get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
 __alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
 alloc_slab_page+0x5d/0x170 mm/slub.c:1876
 allocate_slab mm/slub.c:2023 [inline]
 new_slab+0x87/0x2e0 mm/slub.c:2076
 ___slab_alloc+0xc6d/0x12f0 mm/slub.c:3230
 __slab_alloc mm/slub.c:3329 [inline]
 __slab_alloc_node mm/slub.c:3382 [inline]
 slab_alloc_node mm/slub.c:3475 [inline]
 __kmem_cache_alloc_node+0x1a2/0x260 mm/slub.c:3524
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc_node_track_caller+0xa2/0x230 mm/slab_common.c:1027
 kmalloc_reserve+0x117/0x260 net/core/skbuff.c:581
 pskb_expand_head+0x185/0x1230 net/core/skbuff.c:2099
 netlink_trim+0x180/0x220 net/netlink/af_netlink.c:1305
 netlink_broadcast_filtered+0x80/0x1110 net/netlink/af_netlink.c:1512
 netlink_broadcast net/netlink/af_netlink.c:1557 [inline]
 nlmsg_multicast include/net/netlink.h:1079 [inline]
 nlmsg_notify+0xf0/0x1a0 net/netlink/af_netlink.c:2580
 netdev_state_change+0xf0/0x150 net/core/dev.c:1410
 linkwatch_do_dev+0x10d/0x160 net/core/link_watch.c:191
 __linkwatch_run_queue+0x40f/0x660 net/core/link_watch.c:244
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1154 [inline]
 free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2429
 discard_slab mm/slub.c:2122 [inline]
 __unfreeze_partials+0x1cf/0x210 mm/slub.c:2662
 put_cpu_partial+0x17c/0x250 mm/slub.c:2738
 __slab_free+0x31d/0x410 mm/slub.c:3686
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xe0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:305
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3485 [inline]
 __kmem_cache_alloc_node+0x13e/0x260 mm/slub.c:3524
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc+0xa4/0x240 mm/slab_common.c:1020
 kmalloc include/linux/slab.h:604 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 fib_create_info+0xa61/0x2460 net/ipv4/fib_semantics.c:1459
 fib_table_insert+0xc7/0x1b50 net/ipv4/fib_trie.c:1217
 fib_magic+0x2c5/0x390 net/ipv4/fib_frontend.c:1118
 fib_add_ifaddr+0x144/0x5e0 net/ipv4/fib_frontend.c:1140
 fib_inetaddr_event+0x140/0x1d0 net/ipv4/fib_frontend.c:1454

Memory state around the buggy address:
 ffff888076805480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888076805500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888076805580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff888076805600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888076805680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================