[v6.1] BUG: unable to handle kernel paging request in ip_route_output_key_hash_rcu

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 882efbdd9d34 Linux 6.1.155
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=152ff9e2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=68aa5a3af1cb953a
dashboard link: https://syzkaller.appspot.com/bug?extid=132e7f07cb8a05d72f21
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ace97ceaac60/disk-882efbdd.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/88315d1cd2fa/vmlinux-882efbdd.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5e607a61f425/Image-882efbdd.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+132e7f...@syzkaller.appspotmail.com

Unable to handle kernel paging request at virtual address ffff7000314d4e00
KASAN: maybe wild-memory-access in range [0xffff80018a6a7000-0xffff80018a6a7007]
Mem abort info:
ESR = 0x0000000096000006
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x06: level 2 translation fault
Data abort info:
ISV = 0, ISS = 0x00000006
CM = 0, WnR = 0
swapper pgtable: 4k pages, 48-bit VAs, pgdp=000000020e267000
[ffff7000314d4e00] pgd=000000023ea47003, p4d=000000023ea47003, pud=000000023ea46003, pmd=0000000000000000
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 7351 Comm: syz.2.959 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : __mkroute_output net/ipv4/route.c:2617 [inline]
pc : ip_route_output_key_hash_rcu+0xe38/0x1e3c net/ipv4/route.c:2845
lr : __mkroute_output net/ipv4/route.c:2608 [inline]
lr : ip_route_output_key_hash_rcu+0xdb8/0x1e3c net/ipv4/route.c:2845
sp : ffff800021036930
x29: ffff800021036980 x28: dfff800000000000 x27: 0000000000000001
x26: 0000000080000000 x25: ffff0000c3112c00 x24: ffff0000d926e620
x23: 0000000000000000 x22: ffff80018a6a7000 x21: ffff0000ceac2000
x20: 0000000000000000 x19: 0000000000000000 x18: 0000000000000000
x17: 0000000000000000 x16: ffff8000082d0e30 x15: 0000000000000002
x14: 0000000000000005 x13: 0000000000ff0100 x12: 0000000000080000
x11: 000000000000137a x10: ffff80002998e000 x9 : ffff80018a6a7000
x8 : 1ffff000314d4e00 x7 : ffff8000103f16ec x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000
x2 : ffff800021036cb0 x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
__mkroute_output net/ipv4/route.c:2617 [inline]
ip_route_output_key_hash_rcu+0xe38/0x1e3c net/ipv4/route.c:2845
ip_route_output_key_hash+0x1a8/0x2ec net/ipv4/route.c:2674
__ip_route_output_key include/net/route.h:137 [inline]
ip_route_output_flow+0x3c/0x160 net/ipv4/route.c:2904
ip_send_unicast_reply+0x6b0/0x1024 net/ipv4/ip_output.c:1736
tcp_v4_send_reset+0x1094/0x1ed0 net/ipv4/tcp_ipv4.c:846
tcp_v4_rcv+0x1e18/0x2464 net/ipv4/tcp_ipv4.c:2142
ip_protocol_deliver_rcu+0x350/0x77c net/ipv4/ip_input.c:205
ip_local_deliver_finish+0x250/0x48c net/ipv4/ip_input.c:233
NF_HOOK+0x2c4/0x358 include/linux/netfilter.h:302
ip_local_deliver+0x120/0x194 net/ipv4/ip_input.c:254
dst_input include/net/dst.h:463 [inline]
ip_rcv_finish+0x220/0x24c net/ipv4/ip_input.c:449
NF_HOOK+0x2c4/0x358 include/linux/netfilter.h:302
ip_rcv+0x7c/0x9c net/ipv4/ip_input.c:569
__netif_receive_skb_one_core net/core/dev.c:5581 [inline]
__netif_receive_skb+0xcc/0x2ac net/core/dev.c:5695
netif_receive_skb_internal net/core/dev.c:5781 [inline]
netif_receive_skb+0x1e8/0x8f0 net/core/dev.c:5840
tun_rx_batched+0x478/0x5b4 drivers/net/tun.c:-1
tun_get_user+0x1fa0/0x3240 drivers/net/tun.c:1998
tun_chr_write_iter+0xfc/0x204 drivers/net/tun.c:2044
call_write_iter include/linux/fs.h:2265 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x5ac/0x7c4 fs/read_write.c:584
ksys_write+0x120/0x210 fs/read_write.c:637
__do_sys_write fs/read_write.c:649 [inline]
__se_sys_write fs/read_write.c:646 [inline]
__arm64_sys_write+0x7c/0x90 fs/read_write.c:646
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Code: d538d089 8b080136 d343fec8 aa1703f4 (387c6908)
---[ end trace 0000000000000000 ]---
pstore: crypto_comp_compress failed, ret = -22!
----------------
Code disassembly (best guess):
0: d538d089 mrs x9, tpidr_el1
4: 8b080136 add x22, x9, x8
8: d343fec8 lsr x8, x22, #3
c: aa1703f4 mov x20, x23
* 10: 387c6908 ldrb w8, [x8, x28] <-- trapping instruction


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