UBSAN: array-index-out-of-bounds in sctp_new_state

Status: upstream: reported C repro on 2026/09/16 09:13
Reported-by: syzbot+86979a5a93c14e14855c@syzkaller.appspotmail.com
First crash: 4d23h, last: 1d07h

Sample crash report:
================================================================================
UBSAN: array-index-out-of-bounds in net/netfilter/nf_conntrack_proto_sctp.c:252:2
index 10 is out of range for type 'const char *const[9]'
CPU: 1 PID: 4323 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <IRQ>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 ubsan_epilogue+0xa/0x30 lib/ubsan.c:151
 __ubsan_handle_out_of_bounds+0xdf/0xf0 lib/ubsan.c:282
 sctp_new_state+0x546/0x570 net/netfilter/nf_conntrack_proto_sctp.c:254
 nf_conntrack_sctp_packet+0x1678/0x2e50 net/netfilter/nf_conntrack_proto_sctp.c:469
 nf_conntrack_handle_packet net/netfilter/nf_conntrack_core.c:1918 [inline]
 nf_conntrack_in+0xc6b/0x17b0 net/netfilter/nf_conntrack_core.c:1991
 nf_hook_entry_hookfn include/linux/netfilter.h:142 [inline]
 nf_hook_slow+0xb9/0x200 net/netfilter/core.c:584
 nf_hook+0x205/0x360 include/linux/netfilter.h:257
 NF_HOOK include/linux/netfilter.h:300 [inline]
 ip6_xmit+0xfa5/0x16e0 net/ipv6/ip6_output.c:340
 sctp_v6_xmit+0x94a/0x1150 net/sctp/ipv6.c:250
 sctp_packet_transmit+0x234b/0x28c0 net/sctp/output.c:652
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1492 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1199 [inline]
 sctp_do_sm+0x18cf/0x56a0 net/sctp/sm_sideeffect.c:1170
 sctp_endpoint_bh_rcv+0x56f/0x7b0 net/sctp/endpointola.c:402
 sctp_rcv+0x11a9/0x1690 net/sctp/input.c:258
 sctp6_rcv+0x35/0x60 net/sctp/ipv6.c:1111
 ip6_protocol_deliver_rcu+0x97b/0x1360 net/ipv6/ip6_input.c:425
 ip6_input_finish+0xa2/0x130 net/ipv6/ip6_input.c:466
 NF_HOOK+0x303/0x390 include/linux/netfilter.h:302
 NF_HOOK+0x303/0x390 include/linux/netfilter.h:302
 __netif_receive_skb_one_core net/core/dev.c:5551 [inline]
 __netif_receive_skb+0xcc/0x290 net/core/dev.c:5665
 process_backlog+0x366/0x770 net/core/dev.c:6542
 __napi_poll+0xbb/0x430 net/core/dev.c:7101
 napi_poll net/core/dev.c:7168 [inline]
 net_rx_action+0x522/0xa80 net/core/dev.c:7258
 handle_softirqs+0x336/0x830 kernel/softirq.c:576
 do_softirq+0x142/0x210 kernel/softirq.c:477
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x180/0x1c0 kernel/softirq.c:401
 rcu_read_unlock_bh include/linux/rcupdate.h:810 [inline]
 ip6_finish_output2+0x1205/0x1640 net/ipv6/ip6_output.c:133
 dst_output include/net/dst.h:452 [inline]
 NF_HOOK include/linux/netfilter.h:302 [inline]
 ip6_xmit+0x1089/0x16e0 net/ipv6/ip6_output.c:340
 sctp_v6_xmit+0x94a/0x1150 net/sctp/ipv6.c:250
 sctp_packet_transmit+0x234b/0x28c0 net/sctp/output.c:652
 sctp_outq_flush_transports net/sctp/outqueue.c:1171 [inline]
 sctp_outq_flush+0x1868/0x32b0 net/sctp/outqueue.c:1219
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:-1 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1199 [inline]
 sctp_do_sm+0x4f95/0x56a0 net/sctp/sm_sideeffect.c:1170
 sctp_primitive_REQUESTHEARTBEAT+0x94/0xc0 net/sctp/primitive.c:185
 sctp_apply_peer_addr_params+0xd4/0x1870 net/sctp/socket.c:2439
 sctp_setsockopt_peer_addr_params+0x6b9/0x980 net/sctp/socket.c:2689
 sctp_setsockopt+0x4cd/0xf80 net/sctp/socket.c:4640
 __sys_setsockopt+0x2bf/0x3d0 net/socket.c:2213
 __do_sys_setsockopt net/socket.c:2224 [inline]
 __se_sys_setsockopt net/socket.c:2221 [inline]
 __x64_sys_setsockopt+0xb1/0xc0 net/socket.c:2221
 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: 0033:0x7f632bb52159
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:00007ffe822ac7b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007f632bdd9fa0 RCX: 00007f632bb52159
RDX: 0000000000000009 RSI: 0000000000000084 RDI: 0000000000000004
RBP: 00007f632bbe906b R08: 000000000000009c R09: 0000000000000000
R10: 0000200000000340 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f632bdd9fac R14: 00007f632bdd9fa0 R15: 00007f632bdd9fa0
 </TASK>
================================================================================

Crashes (10):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/16 19:19 linux-5.15.y 0248c33e835e 12a0a44a .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: array-index-out-of-bounds in sctp_new_state
2026/09/20 01:17 linux-5.15.y 0248c33e835e 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: array-index-out-of-bounds in sctp_new_state
2026/09/19 11:55 linux-5.15.y 0248c33e835e 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: array-index-out-of-bounds in sctp_new_state
2026/09/18 12:34 linux-5.15.y 0248c33e835e 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: array-index-out-of-bounds in sctp_new_state
2026/09/18 12:34 linux-5.15.y 0248c33e835e 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: array-index-out-of-bounds in sctp_new_state
2026/09/17 03:31 linux-5.15.y 0248c33e835e 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: array-index-out-of-bounds in sctp_new_state
2026/09/16 20:21 linux-5.15.y 0248c33e835e 12a0a44a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: array-index-out-of-bounds in sctp_new_state
2026/09/16 20:21 linux-5.15.y 0248c33e835e 12a0a44a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: array-index-out-of-bounds in sctp_new_state
2026/09/16 09:12 linux-5.15.y 0248c33e835e 12a0a44a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: array-index-out-of-bounds in sctp_new_state
2026/09/16 09:12 linux-5.15.y 0248c33e835e 12a0a44a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: array-index-out-of-bounds in sctp_new_state
* Struck through repros no longer work on HEAD.