syzbot

==================================================================
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 ffff888026634751 by task syz.1.2332/12097

CPU: 1 PID: 12097 Comm: syz.1.2332 Not tainted 6.6.99-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/0x200 mm/kasan/report.c:466
 kasan_report+0x117/0x150 mm/kasan/report.c:579
 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
 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_outq_flush_transports net/sctp/outqueue.c:1173 [inline]
 sctp_outq_flush+0xecc/0x3100 net/sctp/outqueue.c:1221
 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_REQUESTHEARTBEAT+0x98/0xc0 net/sctp/primitive.c:185
 sctp_apply_peer_addr_params+0xdf/0x1880 net/sctp/socket.c:2437
 sctp_setsockopt_peer_addr_params+0x673/0x940 net/sctp/socket.c:2687
 sctp_setsockopt+0x708/0x11e0 net/sctp/socket.c:4638
 do_sock_setsockopt+0x175/0x1a0 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+0x184/0x200 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: 0033:0x7f64f378e9a9
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:00007f64f4669038 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007f64f39b5fa0 RCX: 00007f64f378e9a9
RDX: 0000000000000009 RSI: 0000000000000084 RDI: 0000000000000003
RBP: 00007f64f3810d69 R08: 000000000000009c R09: 0000000000000000
R10: 00002000000000c0 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f64f39b5fa0 R15: 00007ffc4afad858
 </TASK>

Allocated by task 2:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:328
 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]
 slab_alloc mm/slub.c:3493 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3500 [inline]
 kmem_cache_alloc+0x11e/0x2e0 mm/slub.c:3509
 kmem_cache_zalloc include/linux/slab.h:711 [inline]
 copy_signal+0x50/0x680 kernel/fork.c:1858
 copy_process+0x1673/0x3d70 kernel/fork.c:2503
 kernel_clone+0x21b/0x840 kernel/fork.c:2914
 kernel_thread+0x10d/0x160 kernel/fork.c:2976
 create_kthread kernel/kthread.c:411 [inline]
 kthreadd+0x560/0x730 kernel/kthread.c:766
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

The buggy address belongs to the object at ffff888026634380
 which belongs to the cache signal_cache of size 1544
The buggy address is located 977 bytes inside of
 freed 1544-byte region [ffff888026634380, ffff888026634988)

The buggy address belongs to the physical page:
page:ffffea0000998c00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888026633cc0 pfn:0x26630
head:ffffea0000998c00 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff88807938da01
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888019a4c780 ffffea0000afe410 ffffea0000866610
raw: ffff888026633cc0 0000000000120004 00000001ffffffff ffff88807938da01
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 11, tgid 11 (kworker/u4:0), ts 9513715026, free_ts 0
 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]
 slab_alloc mm/slub.c:3493 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3500 [inline]
 kmem_cache_alloc+0x1b7/0x2e0 mm/slub.c:3509
 kmem_cache_zalloc include/linux/slab.h:711 [inline]
 copy_signal+0x50/0x680 kernel/fork.c:1858
 copy_process+0x1673/0x3d70 kernel/fork.c:2503
 kernel_clone+0x21b/0x840 kernel/fork.c:2914
 user_mode_thread+0xde/0x130 kernel/fork.c:2992
 call_usermodehelper_exec_work+0x5c/0x220 kernel/umh.c:172
 process_one_work kernel/workqueue.c:2634 [inline]
 process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888026634600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888026634680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888026634700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff888026634780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888026634800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================