syzbot


BUG: unable to handle kernel paging request in ip_route_output_key_hash_rcu

Status: upstream: reported C repro on 2025/10/13 20:16
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+132e7f07cb8a05d72f21@syzkaller.appspotmail.com
First crash: 50d, last: 44d
Fix bisection: failed (error log, bisect log)
  
Bug presence (1)
Date Name Commit Repro Result
2025/10/20 upstream (ToT) 211ddde0823f C [report] BUG: unable to handle kernel paging request in ip_route_output_key_hash_rcu
Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KMSAN: uninit-value in ip_route_output_key_hash_rcu (4) net 7 2 1766d 1784d 0/29 auto-closed as invalid on 2021/06/01 04:17
upstream KMSAN: kernel-infoleak in copyout (2) net 17 C 6723 909d 2077d 22/29 fixed on 2023/06/08 14:41
upstream KMSAN: uninit-value in ip_route_output_key_hash_rcu (5) net 7 1 1464d 1464d 0/29 auto-closed as invalid on 2022/02/28 08:56
upstream general protection fault in ip_route_output_key_hash_rcu (2) net 2 2 550d 561d 0/29 closed as invalid on 2024/07/26 12:16
upstream general protection fault in ip_route_output_key_hash_rcu (3) net 7 4 280d 306d 28/29 fixed on 2025/06/10 16:19
upstream KMSAN: kernel-infoleak in _copy_to_iter (7) net 23 C 138977 1013d 1365d 22/29 fixed on 2023/02/24 13:50
upstream KMSAN: uninit-value in IP6_ECN_decapsulate net 7 C 981 714d 2630d 25/29 fixed on 2023/12/21 03:45

Sample crash report:
Unable to handle kernel paging request at virtual address ffff7000314d9000
KASAN: maybe wild-memory-access in range [0xffff80018a6c8000-0xffff80018a6c8007]
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
[ffff7000314d9000] pgd=000000023ea47003, p4d=000000023ea47003, pud=000000023ea46003, pmd=0000000000000000
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 4455 Comm: syz.0.19 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 : ffff800020ce6d70
x29: ffff800020ce6dc0 x28: dfff800000000000 x27: 0000000000000001
x26: 0000000080000000 x25: ffff0000da071800 x24: ffff0000d4f0c620
x23: 0000000000000000 x22: ffff80018a6c8000 x21: ffff0000eba74000
x20: 0000000000000000 x19: 0000000000000000 x18: 0000000000000000
x17: 0000000000000000 x16: ffff8000082d1108 x15: 0000000000000000
x14: 0000000000000005 x13: 0000000000ff0100 x12: 0000000000ff0100
x11: ff008000103ee348 x10: 0000000000000000 x9 : ffff80018a6c8000
x8 : 1ffff000314d9000 x7 : ffff800010537c4c x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000002
x2 : 0000000000000008 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
 icmp_route_lookup+0x384/0x798 net/ipv4/icmp.c:512
 __icmp_send+0xa90/0xfc4 net/ipv4/icmp.c:748
 icmp_send include/net/icmp.h:43 [inline]
 ip_options_compile+0x80/0xbc net/ipv4/ip_options.c:473
 ip_rcv_options net/ipv4/ip_input.c:281 [inline]
 ip_rcv_finish_core+0xbbc/0x18f0 net/ipv4/ip_input.c:387
 ip_rcv_finish+0x130/0x24c net/ipv4/ip_input.c:447
 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 ]---
----------------
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

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/10/20 06:08 linux-6.1.y 8e6e2188d949 1c8c8cd8 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 BUG: unable to handle kernel paging request in ip_route_output_key_hash_rcu
2025/10/20 03:20 linux-6.1.y 8e6e2188d949 1c8c8cd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 BUG: unable to handle kernel paging request in ip_route_output_key_hash_rcu
2025/10/13 20:15 linux-6.1.y 882efbdd9d34 b6605ba8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 BUG: unable to handle kernel paging request in ip_route_output_key_hash_rcu
* Struck through repros no longer work on HEAD.