Subject: Re: [PATCH] IPv6: Fix kernel panic while send SCTP data with IP fragments

From: Wei Yongjun <[email-masked]>
Date: Mon, 20 Aug 2007 10:27:36 +0800

Hi Arnaldo Carvalho de Melo:
> Em Mon, Aug 20, 2007 at 09:28:27AM +0800, Wei Yongjun escreveu:
>   
>> If ICMP6 message with "Packet Too Big" is received after send SCTP DATA,
>> kernel panic will occur when SCTP DATA is send again.
>>
>> This is because of a bad dest address when call to skb_copy_bits().
>>
>> The messages sequence is like this:
>>
>> Endpoint A                             Endpoint B
>>                                <-------  SCTP DATA (size=1432) 
>> ICMP6 message ------->
>> (Packet Too Big pmtu=1280)
>>                                <-------  Resend SCTP DATA (size=1432) 
>> ------------kernel panic---------------
>>     
>
> Thanks! I'm to blame for this one, problem was introduced in:
>
> b0e380b1d8a8e0aca215df97702f99815f05c094
>
> @@ -761,7 +762,7 @@ slow_path:
>                 /*
>                  *      Copy a block of the IP datagram.
>                  */
> -               if (skb_copy_bits(skb, ptr, frag->h.raw, len))
> +               if (skb_copy_bits(skb, ptr, skb_transport_header(skb),
> len))
>                         BUG();
>                 left -= len;
>
> So please add:
>
> Signed-off-by: Arnaldo Carvalho de Melo <[email-masked]>
>
> To this patch.
>
> - Arnaldo
>
>  
>   
>>  printing eip:
>> c05be62a
>> *pde = 00000000
>> Oops: 0002 [#1]
>> SMP
>> Modules linked in: scomm l2cap bluetooth ipv6 dm_mirror dm_mod video output sbs battery lp floppy sg i2c_piix4 i2c_core pcnet32 mii button ac parport_pc parport ide_cd cdrom serio_raw mptspi mptscsih mptbase scsi_transport_spi sd_mod scsi_mod ext3 jbd ehci_hcd ohci_hcd uhci_hcd
>> CPU:    0
>> EIP:    0060:[<c05be62a>]    Not tainted VLI
>> EFLAGS: 00010282   (2.6.23-rc2 #1)
>> EIP is at skb_copy_bits+0x4f/0x1ef
>> eax: 000004d0   ebx: ce12a980   ecx: 00000134   edx: cfd5a880
>> esi: c8246858   edi: 00000000   ebp: c0759b14   esp: c0759adc
>> ds: 007b   es: 007b   fs: 00d8  gs: 0000  ss: 0068
>> Process swapper (pid: 0, ti=c0759000 task=c06d0340 task.ti=c0713000)
>> Stack: c0759b88 c0405867 ce12a980 c8bff838 c789c084 00000000 00000028 cfd5a880
>>        d09f1890 000005dc 0000007b ce12a980 cfd5a880 c8bff838 c0759b88 d09bc521
>>        000004d0 fffff96c 00000200 00000100 c0759b50 cfd5a880 00000246 c0759bd4
>> Call Trace:
>>  [<c0405e1d>] show_trace_log_lvl+0x1a/0x2f
>>  [<c0405ecd>] show_stack_log_lvl+0x9b/0xa3
>>  [<c040608d>] show_registers+0x1b8/0x289
>>  [<c0406271>] die+0x113/0x246
>>  [<c0625dbc>] do_page_fault+0x4ad/0x57e
>>  [<c0624642>] error_code+0x72/0x78
>>  [<d09bc521>] ip6_output+0x8e5/0xab2 [ipv6]
>>  [<d09bcec1>] ip6_xmit+0x2ea/0x3a3 [ipv6]
>>  [<d0a3f2ca>] sctp_v6_xmit+0x248/0x253 [sctp]
>>  [<d0a3c934>] sctp_packet_transmit+0x53f/0x5ae [sctp]
>>  [<d0a34bf8>] sctp_outq_flush+0x555/0x587 [sctp]
>>  [<d0a34d3c>] sctp_retransmit+0xf8/0x10f [sctp]
>>  [<d0a3d183>] sctp_icmp_frag_needed+0x57/0x5b [sctp]
>>  [<d0a3ece2>] sctp_v6_err+0xcd/0x148 [sctp]
>>  [<d09cf1ce>] icmpv6_notify+0xe6/0x167 [ipv6]
>>  [<d09d009a>] icmpv6_rcv+0x7d7/0x849 [ipv6]
>>  [<d09be240>] ip6_input+0x1dc/0x310 [ipv6]
>>  [<d09be965>] ipv6_rcv+0x294/0x2df [ipv6]
>>  [<c05c3789>] netif_receive_skb+0x2d2/0x335
>>  [<c05c5733>] process_backlog+0x7f/0xd0
>>  [<c05c58f6>] net_rx_action+0x96/0x17e
>>  [<c042e722>] __do_softirq+0x64/0xcd
>>  [<c0406f37>] do_softirq+0x5c/0xac
>>  =======================
>> Code: 00 00 29 ca 89 d0 2b 45 e0 89 55 ec 85 c0 7e 35 39 45 08 8b 55 e4 0f 4e 45 08 8b 75 e0 8b 7d dc 89 c1 c1 e9 02 03 b2 a0 00 00 00 <f3> a5 89 c1 83 e1 03 74 02 f3 a4 29 45 08 0f 84 7b 01 00 00 01
>> EIP: [<c05be62a>] skb_copy_bits+0x4f/0x1ef SS:ESP 0068:c0759adc
>> Kernel panic - not syncing: Fatal exception in interrupt
>>
>> Following is the patch.
>>     
Have changed. Thanks

Regards

Signed-off-by: Wei Yongjun <[email-masked]>
Signed-off-by: Arnaldo Carvalho de Melo <[email-masked]>

--- a/net/ipv6/ip6_output.c	2007-08-14 10:36:03.000000000 -0400
+++ b/net/ipv6/ip6_output.c	2007-08-17 15:33:35.000000000 -0400
@@ -794,7 +794,7 @@ slow_path:
 		/*
 		 *	Copy a block of the IP datagram.
 		 */
-		if (skb_copy_bits(skb, ptr, skb_transport_header(skb), len))
+		if (skb_copy_bits(skb, ptr, skb_transport_header(frag), len))
 			BUG();
 		left -= len;