[syzbot] [net?] UBSAN: shift-out-of-bounds in xfrm_selector_match (3)

[syzbot <syzbot+9383b1ff0df4b29ca5e6@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    2b07ea76fd28 Merge tag 'core-urgent-2026-06-13' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11cb4986580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4e828c596d7aa593
dashboard link: https://syzkaller.appspot.com/bug?extid=9383b1ff0df4b29ca5e6
compiler:       Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a90e4670c989/disk-2b07ea76.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e1ad8b2531b9/vmlinux-2b07ea76.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9a927176c534/bzImage-2b07ea76.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9383b1ff0df4b29ca5e6@syzkaller.appspotmail.com

------------[ cut here ]------------
UBSAN: shift-out-of-bounds in ./include/net/xfrm.h:970:23
shift exponent -96 is negative
CPU: 1 UID: 0 PID: 12115 Comm: syz.5.2221 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 ubsan_epilogue+0xa/0x30 lib/ubsan.c:233
 __ubsan_handle_shift_out_of_bounds+0x36d/0x400 lib/ubsan.c:494
 addr4_match include/net/xfrm.h:970 [inline]
 __xfrm4_selector_match net/xfrm/xfrm_policy.c:222 [inline]
 xfrm_selector_match+0xd5c/0x1140 net/xfrm/xfrm_policy.c:247
 __xfrm_policy_check+0x5d1/0x37b0 net/xfrm/xfrm_policy.c:3715
 __xfrm_policy_check2 include/net/xfrm.h:1302 [inline]
 xfrm_policy_check+0x475/0x880 include/net/xfrm.h:1307
 vti_rcv_cb+0x3b6/0x770 net/ipv4/ip_vti.c:135
 tunnel4_rcv_cb+0xd6/0x230 net/ipv4/tunnel4.c:124
 xfrm_rcv_cb+0x1c7/0x310 net/xfrm/xfrm_input.c:117
 xfrm_input+0x4738/0x7760 net/xfrm/xfrm_input.c:729
 vti_input+0x21f/0x330 net/ipv4/ip_vti.c:69
 tunnel4_rcv+0xdd/0x2d0 net/ipv4/tunnel4.c:103
 ip_protocol_deliver_rcu+0x2dc/0x440 net/ipv4/ip_input.c:207
 ip_local_deliver_finish+0x3bb/0x6f0 net/ipv4/ip_input.c:241
 NF_HOOK+0x336/0x3c0 include/linux/netfilter.h:318
 NF_HOOK+0x336/0x3c0 include/linux/netfilter.h:318
 __netif_receive_skb_one_core net/core/dev.c:6202 [inline]
 __netif_receive_skb net/core/dev.c:6315 [inline]
 netif_receive_skb_internal net/core/dev.c:6401 [inline]
 netif_receive_skb+0x45b/0xbf0 net/core/dev.c:6460
 tun_rx_batched+0x1de/0x790 drivers/net/tun.c:1487
 tun_get_user+0x2b04/0x4350 drivers/net/tun.c:1955
 tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:2001
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x612/0xba0 fs/read_write.c:688
 ksys_write+0x150/0x270 fs/read_write.c:740
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fca8819ce59
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:00007fca890f6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fca88416090 RCX: 00007fca8819ce59
RDX: 0000000000000fce RSI: 0000200000000840 RDI: 0000000000000003
RBP: 00007fca88232d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fca88416128 R14: 00007fca88416090 R15: 00007fca8853fa48
 </TASK>
---[ end trace ]---


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