general protection fault in ip6_pol_route

[YAN KANG]

Dear maintainers,

I found a kernel  bug titiled "general protection fault in ip6_pol_route" while using modified syzkaller fuzzing tool. I Itested it on the latest Linux upstream version (6.13.0-rc7) .


After preliminary analysis, the rootcause may be in ip6_pol_route function  net/ipv6/route.c
    res is a stack object.    [1]
    fib6_select_path(net, &res, fl6, oif, false, skb, strict)  call  may initialize res->nh.[2]
    rt = rt6_get_pcpu_route( &res);   [3]
           pcpu_rt = this_cpu_read(*res->nh->rt6i_pcpu); // *res->nh is NULL, crash

   in [2], res->nh can be initialized in several ways,possibly one of which initializes it to NULL.

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

If you fix this issue, please add the following tag to the commit:
Reported-by: yan kang <kangyan91@xxxxxxxxxxx>
Reported-by: yue sun <samsun1006219@xxxxxxxxx


I hope it helps.
Best regards
yan kang

Kernel crash log is listed below.

==================================================================
crash log
==================================================================

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000013: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000098-0x000000000000009f]
CPU: 1 UID: 0 PID: 12 Comm: kworker/u8:1 Not tainted 6.13.0-rc7-00003-gd4774759e15b-dirty #87
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
Workqueue: ipv6_addrconf addrconf_dad_work
RIP: 0010:rt6_get_pcpu_route net/ipv6/route.c:1411 [inline]
RIP: 0010:ip6_pol_route+0x3be/0x1210 net/ipv6/route.c:2264
Code: f7 4d 85 f6 0f 84 40 03 00 00 e8 3d 8f cb f7 49 8d be 98 00 00 00 4c 89 f3 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 1a 0d 00 00 45 8b ae 98 00 00
RSP: 0018:ffffc900001e87d0 EFLAGS: 00010203
RAX: dffffc0000000000 RBX: 0000000000000004 RCX: ffffffff89cd3195
RDX: 0000000000000013 RSI: ffffffff89cd31a3 RDI: 000000000000009c
RBP: ffff88812a010000 R08: 0000000000000001 R09: ffff888110288000
R10: 0000000000000004 R11: 0000000000000000 R12: 0000000000000080
R13: ffffc900001e8b20 R14: 0000000000000004 R15: ffffc900001e8860
FS:  0000000000000000(0000) GS:ffff888135e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc23d35b344 CR3: 000000010570e000 CR4: 0000000000752ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
 <IRQ>
 pol_lookup_func include/net/ip6_fib.h:616 [inline]
 fib6_rule_lookup+0x538/0x720 net/ipv6/fib6_rules.c:117
 ip6_route_input_lookup net/ipv6/route.c:2300 [inline]
 ip6_route_input+0x66e/0xc20 net/ipv6/route.c:2596
 ip6_rcv_finish_core.constprop.0+0x1aa/0x5e0 net/ipv6/ip6_input.c:66
 ip6_rcv_finish net/ipv6/ip6_input.c:77 [inline]
 NF_HOOK include/linux/netfilter.h:314 [inline]
 NF_HOOK include/linux/netfilter.h:308 [inline]
 ipv6_rcv+0x1e7/0x690 net/ipv6/ip6_input.c:309
 __netif_receive_skb_one_core+0x12e/0x1f0 net/core/dev.c:5672
 __netif_receive_skb+0x1d/0x150 net/core/dev.c:5785
 process_backlog+0x319/0x1460 net/core/dev.c:6117
 __napi_poll.constprop.0+0xb6/0x540 net/core/dev.c:6877
 napi_poll net/core/dev.c:6946 [inline]
 net_rx_action+0x9d2/0xe30 net/core/dev.c:7068
 handle_softirqs+0x1bf/0x850 kernel/softirq.c:554
 do_softirq kernel/softirq.c:455 [inline]
 do_softirq+0xac/0xe0 kernel/softirq.c:442
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x100/0x120 kernel/softirq.c:382
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 rcu_read_unlock_bh include/linux/rcupdate.h:919 [inline]
 __dev_queue_xmit+0x1b98/0x4160 net/core/dev.c:4461
 dev_queue_xmit include/linux/netdevice.h:3168 [inline]
 neigh_resolve_output net/core/neighbour.c:1514 [inline]
 neigh_resolve_output+0x58e/0x900 net/core/neighbour.c:1494
 neigh_output include/net/neighbour.h:539 [inline]
 ip6_finish_output2+0xae5/0x1ec0 net/ipv6/ip6_output.c:141
 __ip6_finish_output net/ipv6/ip6_output.c:215 [inline]
 ip6_finish_output+0x713/0x1230 net/ipv6/ip6_output.c:226
 NF_HOOK_COND include/linux/netfilter.h:303 [inline]
 ip6_output+0x203/0x550 net/ipv6/ip6_output.c:247
 dst_output include/net/dst.h:450 [inline]
 NF_HOOK include/linux/netfilter.h:314 [inline]
 ndisc_send_skb+0xa65/0x1c70 net/ipv6/ndisc.c:511
 ndisc_send_ns+0xb5/0x130 net/ipv6/ndisc.c:669
 addrconf_dad_work+0xd3a/0x1610 net/ipv6/addrconf.c:4303
 process_one_work+0x99f/0x1bb0 kernel/workqueue.c:3229
 process_scheduled_works kernel/workqueue.c:3310 [inline]
 worker_thread+0x66e/0xe80 kernel/workqueue.c:3391
 kthread+0x2c7/0x3b0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:rt6_get_pcpu_route net/ipv6/route.c:1411 [inline]
RIP: 0010:ip6_pol_route+0x3be/0x1210 net/ipv6/route.c:2264
Code: f7 4d 85 f6 0f 84 40 03 00 00 e8 3d 8f cb f7 49 8d be 98 00 00 00 4c 89 f3 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 1a 0d 00 00 45 8b ae 98 00 00
RSP: 0018:ffffc900001e87d0 EFLAGS: 00010203
RAX: dffffc0000000000 RBX: 0000000000000004 RCX: ffffffff89cd3195
RDX: 0000000000000013 RSI: ffffffff89cd31a3 RDI: 000000000000009c
RBP: ffff88812a010000 R08: 0000000000000001 R09: ffff888110288000
R10: 0000000000000004 R11: 0000000000000000 R12: 0000000000000080
R13: ffffc900001e8b20 R14: 0000000000000004 R15: ffffc900001e8860
FS:  0000000000000000(0000) GS:ffff888135e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc23d35b344 CR3: 000000010570e000 CR4: 0000000000752ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400
PKRU: 55555554
----------------
Code disassembly (best guess):
   0:	f7 4d 85 f6 0f 84 40 	testl  $0x40840ff6,-0x7b(%rbp)
   7:	03 00                	add    (%rax),%eax
   9:	00 e8                	add    %ch,%al
   b:	3d 8f cb f7 49       	cmp    $0x49f7cb8f,%eax
  10:	8d be 98 00 00 00    	lea    0x98(%rsi),%edi
  16:	4c 89 f3             	mov    %r14,%rbx
  19:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  20:	fc ff df
  23:	48 89 fa             	mov    %rdi,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	0f b6 04 02          	movzbl (%rdx,%rax,1),%eax <-- trapping instruction
  2e:	84 c0                	test   %al,%al
  30:	74 08                	je     0x3a
  32:	3c 03                	cmp    $0x3,%al
  34:	0f 8e 1a 0d 00 00    	jle    0xd54
  3a:	45                   	rex.RB
  3b:	8b                   	.byte 0x8b
  3c:	ae                   	scas   %es:(%rdi),%al
  3d:	98                   	cwtl