[syzbot] [net?] kernel BUG in set_ipsecrequest

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 48a97ffc6c82 bpf: Consistently use bpf_rcu_lock_held() eve..
git tree: bpf-next
console output: https://syzkaller.appspot.com/x/log.txt?x=144d0734580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9ad7b090a18654a7
dashboard link: https://syzkaller.appspot.com/bug?extid=be97dd4da14ae88b6ba4
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16f7e5e2580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11ecec58580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/87ffd600eff3/disk-48a97ffc.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/aa84f0e32430/vmlinux-48a97ffc.xz
kernel image: https://storage.googleapis.com/syzbot-assets/16498048e16c/bzImage-48a97ffc.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+be97dd...@syzkaller.appspotmail.com

skbuff: skb_over_panic: text:ffffffff8a1fdd63 len:392 put:16 head:ffff888073664d00 data:ffff888073664d00 tail:0x188 end:0x180 dev:<NULL>
------------[ cut here ]------------
kernel BUG at net/core/skbuff.c:212!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 1 UID: 0 PID: 6012 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:skb_panic+0x157/0x160 net/core/skbuff.c:212
Code: c7 60 10 6e 8c 48 8b 74 24 08 48 8b 54 24 10 8b 0c 24 44 8b 44 24 04 4d 89 e9 50 55 41 57 41 56 e8 6e 54 f5 ff 48 83 c4 20 90 <0f> 0b cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90003d5eb68 EFLAGS: 00010282
RAX: 0000000000000088 RBX: dffffc0000000000 RCX: bc84b821dc35fd00
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000180 R08: ffffc90003d5e867 R09: 1ffff920007abd0c
R10: dffffc0000000000 R11: fffff520007abd0d R12: ffff8880720b7b50
R13: ffff888073664d00 R14: ffff888073664d00 R15: 0000000000000188
FS: 000055555b9e7500(0000) GS:ffff888125e0c000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055555b9e7808 CR3: 000000007ead6000 CR4: 00000000003526f0
Call Trace:
<TASK>
skb_over_panic net/core/skbuff.c:217 [inline]
skb_put+0x159/0x210 net/core/skbuff.c:2583
skb_put_zero include/linux/skbuff.h:2788 [inline]
set_ipsecrequest+0x73/0x680 net/key/af_key.c:3532
pfkey_send_migrate+0x11f2/0x1de0 net/key/af_key.c:3636
km_migrate+0x155/0x260 net/xfrm/xfrm_state.c:2838
xfrm_migrate+0x2020/0x2330 net/xfrm/xfrm_policy.c:4698
xfrm_do_migrate+0x796/0x900 net/xfrm/xfrm_user.c:3144
xfrm_user_rcv_msg+0x7a3/0xab0 net/xfrm/xfrm_user.c:3501
netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2552
xfrm_netlink_rcv+0x79/0x90 net/xfrm/xfrm_user.c:3523
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1896
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg+0x21c/0x270 net/socket.c:742
____sys_sendmsg+0x505/0x830 net/socket.c:2630
___sys_sendmsg+0x21f/0x2a0 net/socket.c:2684
__sys_sendmsg net/socket.c:2716 [inline]
__do_sys_sendmsg net/socket.c:2721 [inline]
__se_sys_sendmsg net/socket.c:2719 [inline]
__x64_sys_sendmsg+0x19b/0x260 net/socket.c:2719
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5fcd58eec9
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:00007ffe59dd1ab8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f5fcd7e5fa0 RCX: 00007f5fcd58eec9
RDX: 0000000000000000 RSI: 0000200000000380 RDI: 0000000000000004
RBP: 00007f5fcd611f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5fcd7e5fa0 R14: 00007f5fcd7e5fa0 R15: 0000000000000003
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:skb_panic+0x157/0x160 net/core/skbuff.c:212
Code: c7 60 10 6e 8c 48 8b 74 24 08 48 8b 54 24 10 8b 0c 24 44 8b 44 24 04 4d 89 e9 50 55 41 57 41 56 e8 6e 54 f5 ff 48 83 c4 20 90 <0f> 0b cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90003d5eb68 EFLAGS: 00010282
RAX: 0000000000000088 RBX: dffffc0000000000 RCX: bc84b821dc35fd00
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000180 R08: ffffc90003d5e867 R09: 1ffff920007abd0c
R10: dffffc0000000000 R11: fffff520007abd0d R12: ffff8880720b7b50
R13: ffff888073664d00 R14: ffff888073664d00 R15: 0000000000000188
FS: 000055555b9e7500(0000) GS:ffff888125e0c000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055555b9e7808 CR3: 000000007ead6000 CR4: 00000000003526f0


---
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[syzbot]

syzbot has bisected this issue to:

commit 14ad6ed30a10afbe91b0749d6378285f4225d482
Author: Paolo Abeni <pab...@redhat.com>
Date: Tue Feb 18 18:29:39 2025 +0000

net: allow small head cache usage with large MAX_SKB_FRAGS values

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=177a35e2580000
start commit: 48a97ffc6c82 bpf: Consistently use bpf_rcu_lock_held() eve..
git tree: bpf-next
final oops: https://syzkaller.appspot.com/x/report.txt?x=14fa35e2580000
console output: https://syzkaller.appspot.com/x/log.txt?x=10fa35e2580000

kernel config: https://syzkaller.appspot.com/x/.config?x=9ad7b090a18654a7
dashboard link: https://syzkaller.appspot.com/bug?extid=be97dd4da14ae88b6ba4

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16f7e5e2580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11ecec58580000

Reported-by: syzbot+be97dd...@syzkaller.appspotmail.com
Fixes: 14ad6ed30a10 ("net: allow small head cache usage with large MAX_SKB_FRAGS values")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection