sctp: avoid running the sctp state machine recursively

Ying triggered a call trace when doing an asconf testing:

  BUG: scheduling while atomic: swapper/12/0/0x10000100
  Call Trace:
   <IRQ>  [<ffffffffa4375904>] dump_stack+0x19/0x1b
   [<ffffffffa436fcaf>] __schedule_bug+0x64/0x72
   [<ffffffffa437b93a>] __schedule+0x9ba/0xa00
   [<ffffffffa3cd5326>] __cond_resched+0x26/0x30
   [<ffffffffa437bc4a>] _cond_resched+0x3a/0x50
   [<ffffffffa3e22be8>] kmem_cache_alloc_node+0x38/0x200
   [<ffffffffa423512d>] __alloc_skb+0x5d/0x2d0
   [<ffffffffc0995320>] sctp_packet_transmit+0x610/0xa20 [sctp]
   [<ffffffffc098510e>] sctp_outq_flush+0x2ce/0xc00 [sctp]
   [<ffffffffc098646c>] sctp_outq_uncork+0x1c/0x20 [sctp]
   [<ffffffffc0977338>] sctp_cmd_interpreter.isra.22+0xc8/0x1460 [sctp]
   [<ffffffffc0976ad1>] sctp_do_sm+0xe1/0x350 [sctp]
   [<ffffffffc099443d>] sctp_primitive_ASCONF+0x3d/0x50 [sctp]
   [<ffffffffc0977384>] sctp_cmd_interpreter.isra.22+0x114/0x1460 [sctp]
   [<ffffffffc0976ad1>] sctp_do_sm+0xe1/0x350 [sctp]
   [<ffffffffc097b3a4>] sctp_assoc_bh_rcv+0xf4/0x1b0 [sctp]
   [<ffffffffc09840f1>] sctp_inq_push+0x51/0x70 [sctp]
   [<ffffffffc099732b>] sctp_rcv+0xa8b/0xbd0 [sctp]

As it shows, the first sctp_do_sm() running under atomic context (NET_RX
softirq) invoked sctp_primitive_ASCONF() that uses GFP_KERNEL flag later,
and this flag is supposed to be used in non-atomic context only. Besides,
sctp_do_sm() was called recursively, which is not expected.

Vlad tried to fix this recursive call in Commit c0786693404c ("sctp: Fix
oops when sending queued ASCONF chunks") by introducing a new command
SCTP_CMD_SEND_NEXT_ASCONF. But it didn't work as this command is still
used in the first sctp_do_sm() call, and sctp_primitive_ASCONF() will
be called in this command again.

To avoid calling sctp_do_sm() recursively, we send the next queued ASCONF
not by sctp_primitive_ASCONF(), but by sctp_sf_do_prm_asconf() in the 1st
sctp_do_sm() directly.

Reported-by: Ying Xu <yinxu@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 0 insertions, 29 deletions

diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
index 1d143bc3f73d..4aa03588f87b 100644
--- a/net/sctp/sm_sideeffect.c
+++ b/net/sctp/sm_sideeffect.c
@@ -1112,32 +1112,6 @@ static void 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)
-{
-	struct net *net = sock_net(asoc->base.sk);
-
-	/* 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(net, 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
  * functionality there.
@@ -1783,9 +1757,6 @@ static int sctp_cmd_interpreter(enum sctp_event_type event_type,
 			}
 			sctp_cmd_send_msg(asoc, cmd->obj.msg, gfp);
 			break;
-		case SCTP_CMD_SEND_NEXT_ASCONF:
-			sctp_cmd_send_asconf(asoc);
-			break;
 		case SCTP_CMD_PURGE_ASCONF_QUEUE:
 			sctp_asconf_queue_teardown(asoc);
 			break;