sctp: Fix oops when sending queued ASCONF chunks

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
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]
[<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 <[e-mail]>
Signed-off-by: Yuansong Qiao <[e-mail]>
Signed-off-by: Shuaijun Zhang <[e-mail]>
Signed-off-by: Vlad Yasevich <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/sctp/command.h

···
 	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;
 

net/sctp/sm_make_chunk.c

···
 	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;
 }
 

net/sctp/sm_sideeffect.c

···
 }
 
 
+/* 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
···
 				local_cork = 1;
 			}
 			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",

net/sctp/sm_statefuns.c

···
 				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));