Subject: Re: [PATCH 5/5] sctp: Fix oops when sending queued ASCONF chunks

From: Shuaijun Zhang <[email-masked]>
Date: Thu, 29 Apr 2010 15:09:20 +0100

Vlad Yasevich wrote:
> When we finish processing ASCONF_ACK chunk, we try to send
> the next queued ASCONF.  This action runs the sctp state
> machine recursively and it's not prepared to do so.
>
> kernel BUG at kernel/timer.c:790!
> invalid opcode: 0000 [#1] SMP
> last sysfs file: /sys/module/ipv6/initstate
> Modules linked in: sha256_generic sctp libcrc32c ipv6 dm_multipath
> uinput 8139too i2c_piix4 8139cp mii i2c_core pcspkr virtio_net joydev
> floppy virtio_blk virtio_pci [last unloaded: scsi_wait_scan]
>
> Pid: 0, comm: swapper Not tainted 2.6.34-rc4 #15 /Bochs
> EIP: 0060:[<c044a2ef>] EFLAGS: 00010286 CPU: 0
> EIP is at add_timer+0xd/0x1b
> EAX: cecbab14 EBX: 000000f0 ECX: c0957b1c EDX: 03595cf4
> ESI: cecba800 EDI: cf276f00 EBP: c0957aa0 ESP: c0957aa0
>  DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
> Process swapper (pid: 0, ti=c0956000 task=c0988ba0 task.ti=c0956000)
> Stack:
>  c0957ae0 d1851214 c0ab62e4 c0ab5f26 0500ffff 00000004 00000005 00000004
> <0> 00000000 d18694fd 00000004 1666b892 cecba800 cecba800 c0957b14
> 00000004
> <0> c0957b94 d1851b11 ceda8b00 cecba800 cf276f00 00000001 c0957b14
> 000000d0
>   
According to the call trace below, it seems that our modification did 
not take affect.
sctp_primitive_ASCONF should be invoked after sctp_side_effects().
Our code fixed the same problem in kernel 2.6.27.28.
Not sure about the difference between 2.6.34-rc4 kernel and 2.6.27.28 
kernel.
> Call Trace:
>  [<d1851214>] ? sctp_side_effects+0x607/0xdfc [sctp]
>  [<d1851b11>] ? sctp_do_sm+0x108/0x159 [sctp]
>  [<d1863386>] ? sctp_pname+0x0/0x1d [sctp]
>  [<d1861a56>] ? sctp_primitive_ASCONF+0x36/0x3b [sctp]		<--- sctp_side_effects() should show up here before send next asconf
>  [<d185657c>] ? sctp_process_asconf_ack+0x2a4/0x2d3 [sctp]
>  [<d184e35c>] ? sctp_sf_do_asconf_ack+0x1dd/0x2b4 [sctp]
>  [<d1851ac1>] ? sctp_do_sm+0xb8/0x159 [sctp]
>  [<d1863334>] ? sctp_cname+0x0/0x52 [sctp]
>  [<d1854377>] ? sctp_assoc_bh_rcv+0xac/0xe1 [sctp]
>  [<d1858f0f>] ? sctp_inq_push+0x2d/0x30 [sctp]
>  [<d186329d>] ? sctp_rcv+0x797/0x82e [sctp]
>
> Tested-by: Wei Yongjun <[email-masked]>
> Signed-off-by: Yuansong Qiao <[email-masked]>
> Signed-off-by: Shuaijun Zhang <[email-masked]>
> Signed-off-by: Vlad Yasevich <[email-masked]>
> ---
>  include/net/sctp/command.h |    1 +
>  net/sctp/sm_make_chunk.c   |   15 ---------------
>  net/sctp/sm_sideeffect.c   |   26 ++++++++++++++++++++++++++
>  net/sctp/sm_statefuns.c    |    8 +++++++-
>  4 files changed, 34 insertions(+), 16 deletions(-)
>
> diff --git a/include/net/sctp/command.h b/include/net/sctp/command.h
> index 8be5135..2c55a7e 100644
> --- a/include/net/sctp/command.h
> +++ b/include/net/sctp/command.h
> @@ -107,6 +107,7 @@ typedef enum {
>  	SCTP_CMD_T1_RETRAN,	 /* Mark for retransmission after T1 timeout  */
>  	SCTP_CMD_UPDATE_INITTAG, /* Update peer inittag */
>  	SCTP_CMD_SEND_MSG,	 /* Send the whole use message */
> +	SCTP_CMD_SEND_NEXT_ASCONF, /* Send the next ASCONF after ACK */
>  	SCTP_CMD_LAST
>  } sctp_verb_t;
>  
> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
> index f6fc5c1..0fd5b4c 100644
> --- a/net/sctp/sm_make_chunk.c
> +++ b/net/sctp/sm_make_chunk.c
> @@ -3318,21 +3318,6 @@ int sctp_process_asconf_ack(struct sctp_association *asoc,
>  	sctp_chunk_free(asconf);
>  	asoc->addip_last_asconf = NULL;
>  
> -	/* Send the next asconf chunk from the addip chunk queue. */
> -	if (!list_empty(&asoc->addip_chunk_list)) {
> -		struct list_head *entry = asoc->addip_chunk_list.next;
> -		asconf = list_entry(entry, struct sctp_chunk, list);
> -
> -		list_del_init(entry);
> -
> -		/* Hold the chunk until an ASCONF_ACK is received. */
> -		sctp_chunk_hold(asconf);
> -		if (sctp_primitive_ASCONF(asoc, asconf))
> -			sctp_chunk_free(asconf);
> -		else
> -			asoc->addip_last_asconf = asconf;
> -	}
> -
>  	return retval;
>  }
>  
> diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
> index 4c5bed9..d5ae450 100644
> --- a/net/sctp/sm_sideeffect.c
> +++ b/net/sctp/sm_sideeffect.c
> @@ -962,6 +962,29 @@ static int sctp_cmd_send_msg(struct sctp_association *asoc,
>  }
>  
>  
> +/* Sent the next ASCONF packet currently stored in the association.
> + * This happens after the ASCONF_ACK was succeffully processed.
> + */
> +static void sctp_cmd_send_asconf(struct sctp_association *asoc)
> +{
> +	/* Send the next asconf chunk from the addip chunk
> +	 * queue.
> +	 */
> +	if (!list_empty(&asoc->addip_chunk_list)) {
> +		struct list_head *entry = asoc->addip_chunk_list.next;
> +		struct sctp_chunk *asconf = list_entry(entry,
> +						struct sctp_chunk, list);
> +		list_del_init(entry);
> +
> +		/* Hold the chunk until an ASCONF_ACK is received. */
> +		sctp_chunk_hold(asconf);
> +		if (sctp_primitive_ASCONF(asoc, asconf))
> +			sctp_chunk_free(asconf);
> +		else
> +			asoc->addip_last_asconf = asconf;
> +	}
> +}
> +
>  
>  /* These three macros allow us to pull the debugging code out of the
>   * main flow of sctp_do_sm() to keep attention focused on the real
> @@ -1617,6 +1640,9 @@ static int sctp_cmd_interpreter(sctp_event_t event_type,
>  			}
>  			error = sctp_cmd_send_msg(asoc, cmd->obj.msg);
>  			break;
> +		case SCTP_CMD_SEND_NEXT_ASCONF:
> +			sctp_cmd_send_asconf(asoc);
> +			break;
>  		default:
>  			printk(KERN_WARNING "Impossible command: %u, %p\n",
>  			       cmd->verb, cmd->obj.ptr);
> diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
> index abf601a..24b2cd5 100644
> --- a/net/sctp/sm_statefuns.c
> +++ b/net/sctp/sm_statefuns.c
> @@ -3676,8 +3676,14 @@ sctp_disposition_t sctp_sf_do_asconf_ack(const struct sctp_endpoint *ep,
>  				SCTP_TO(SCTP_EVENT_TIMEOUT_T4_RTO));
>  
>  		if (!sctp_process_asconf_ack((struct sctp_association *)asoc,
> -					     asconf_ack))
> +					     asconf_ack)) {
> +			/* Successfully processed ASCONF_ACK.  We can
> +			 * release the next asconf if we have one.
> +			 */
> +			sctp_add_cmd_sf(commands, SCTP_CMD_SEND_NEXT_ASCONF,
> +					SCTP_NULL());
>  			return SCTP_DISPOSITION_CONSUME;
> +		}
>  
>  		abort = sctp_make_abort(asoc, asconf_ack,
>  					sizeof(sctp_errhdr_t));
>