[syzbot] [net?] BUG: unable to handle kernel paging request in ip_route_output_key_hash_rcu

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 2eba5e05d9bc Merge tag 'loongarch-fixes-6.18-2' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=125498b4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a1db0fea040c2a9f
dashboard link: https://syzkaller.appspot.com/bug?extid=334190e097a98a1b81bb
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=16ebaa12580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15848e92580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-2eba5e05.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ea041b2f66b0/vmlinux-2eba5e05.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a9a26c9a2a1c/bzImage-2eba5e05.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+334190...@syzkaller.appspotmail.com

BUG: unable to handle page fault for address: ffffed1011ae5e00
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 5ffcd067 P4D 5ffcd067 PUD 2fff7067 PMD 0
Oops: Oops: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5500 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:__mkroute_output net/ipv4/route.c:2649 [inline]
RIP: 0010:ip_route_output_key_hash_rcu+0x12fc/0x23e0 net/ipv4/route.c:2875
Code: 4c 8b 35 2f ea bc 08 49 83 c7 38 4c 89 f8 48 c1 e8 03 80 3c 28 00 74 08 4c 89 ff e8 ce 38 75 f8 4d 03 37 4c 89 f0 48 c1 e8 03 <80> 3c 28 00 74 08 4c 89 f7 e8 b6 38 75 f8 4d 8b 36 e8 9e 72 96 01
RSP: 0018:ffffc9000298e948 EFLAGS: 00010a06
RAX: 1ffff11011ae5e00 RBX: 0000000080000000 RCX: ffff888000bdc900
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: dffffc0000000000 R08: ffff888000bdc900 R09: 0000000000000003
R10: 0000000000000005 R11: 0000000000000000 R12: ffffc9000298ebd3
R13: 0000000000000000 R14: ffff88808d72f000 R15: ffff888036590158
FS: 000055556855e500(0000) GS:ffff88808d72f000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffed1011ae5e00 CR3: 0000000042bac000 CR4: 0000000000352ef0
Call Trace:
<TASK>
ip_route_output_key_hash+0x174/0x280 net/ipv4/route.c:2705
__ip_route_output_key include/net/route.h:169 [inline]
ip_route_output_flow+0x2a/0x150 net/ipv4/route.c:2932
ip_route_output_key include/net/route.h:179 [inline]
sctp_v4_get_dst+0x3c7/0x1200 net/sctp/protocol.c:455
sctp_transport_route+0x118/0x2f0 net/sctp/transport.c:448
sctp_ootb_pkt_new+0x28b/0x3c0 net/sctp/sm_statefuns.c:6437
sctp_sf_abort_violation+0x14b/0xc60 net/sctp/sm_statefuns.c:4771
sctp_sf_violation_chunklen net/sctp/sm_statefuns.c:4830 [inline]
sctp_sf_ootb+0x4df/0x7c0 net/sctp/sm_statefuns.c:-1
sctp_do_sm+0x1e7/0x5a20 net/sctp/sm_sideeffect.c:1172
sctp_endpoint_bh_rcv+0x591/0x7e0 net/sctp/endpointola.c:408
sctp_rcv+0x11dc/0x1870 net/sctp/input.c:243
ip_protocol_deliver_rcu+0x2e0/0x440 net/ipv4/ip_input.c:205
ip_local_deliver_finish+0x3bb/0x6f0 net/ipv4/ip_input.c:239
NF_HOOK+0x30c/0x3a0 include/linux/netfilter.h:318
NF_HOOK+0x30c/0x3a0 include/linux/netfilter.h:318
__netif_receive_skb_one_core net/core/dev.c:6079 [inline]
__netif_receive_skb+0x143/0x380 net/core/dev.c:6192
netif_receive_skb_internal net/core/dev.c:6278 [inline]
netif_receive_skb+0x1cb/0x790 net/core/dev.c:6337
tun_rx_batched+0x1b9/0x730 drivers/net/tun.c:1485
tun_get_user+0x2b65/0x3e90 drivers/net/tun.c:1953
tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1999
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5c9/0xb30 fs/read_write.c:686
ksys_write+0x145/0x250 fs/read_write.c:738
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: 0033:0x7fbd9ab8e1ff
Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 f9 92 02 00 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 31 44 89 c7 48 89 44 24 08 e8 4c 93 02 00 48
RSP: 002b:00007ffca504fd10 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fbd9ade5fa0 RCX: 00007fbd9ab8e1ff
RDX: 0000000000000032 RSI: 00002000000000c0 RDI: 00000000000000c8
RBP: 00007fbd9ac13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000032 R11: 0000000000000293 R12: 0000000000000000
R13: 00007fbd9ade5fa0 R14: 00007fbd9ade5fa0 R15: 0000000000000003
</TASK>
Modules linked in:
CR2: ffffed1011ae5e00
---[ end trace 0000000000000000 ]---
RIP: 0010:__mkroute_output net/ipv4/route.c:2649 [inline]
RIP: 0010:ip_route_output_key_hash_rcu+0x12fc/0x23e0 net/ipv4/route.c:2875
Code: 4c 8b 35 2f ea bc 08 49 83 c7 38 4c 89 f8 48 c1 e8 03 80 3c 28 00 74 08 4c 89 ff e8 ce 38 75 f8 4d 03 37 4c 89 f0 48 c1 e8 03 <80> 3c 28 00 74 08 4c 89 f7 e8 b6 38 75 f8 4d 8b 36 e8 9e 72 96 01
RSP: 0018:ffffc9000298e948 EFLAGS: 00010a06
RAX: 1ffff11011ae5e00 RBX: 0000000080000000 RCX: ffff888000bdc900
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: dffffc0000000000 R08: ffff888000bdc900 R09: 0000000000000003
R10: 0000000000000005 R11: 0000000000000000 R12: ffffc9000298ebd3
R13: 0000000000000000 R14: ffff88808d72f000 R15: ffff888036590158
FS: 000055556855e500(0000) GS:ffff88808d72f000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffed1011ae5e00 CR3: 0000000042bac000 CR4: 0000000000352ef0
----------------
Code disassembly (best guess):
0: 4c 8b 35 2f ea bc 08 mov 0x8bcea2f(%rip),%r14 # 0x8bcea36
7: 49 83 c7 38 add $0x38,%r15
b: 4c 89 f8 mov %r15,%rax
e: 48 c1 e8 03 shr $0x3,%rax
12: 80 3c 28 00 cmpb $0x0,(%rax,%rbp,1)
16: 74 08 je 0x20
18: 4c 89 ff mov %r15,%rdi
1b: e8 ce 38 75 f8 call 0xf87538ee
20: 4d 03 37 add (%r15),%r14
23: 4c 89 f0 mov %r14,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 80 3c 28 00 cmpb $0x0,(%rax,%rbp,1) <-- trapping instruction
2e: 74 08 je 0x38
30: 4c 89 f7 mov %r14,%rdi
33: e8 b6 38 75 f8 call 0xf87538ee
38: 4d 8b 36 mov (%r14),%r14
3b: e8 9e 72 96 01 call 0x19672de


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