[SCTP]: Fix kernel panic while received ASCONF chunk with bad serial number

While recevied ASCONF chunk with serial number less then needed, kernel
will treat this chunk as a retransmitted ASCONF chunk and find cached
ASCONF-ACK chunk used sctp_assoc_lookup_asconf_ack(). But this function
will always return NO-NULL. So response with cached ASCONF-ACKs chunk
will cause kernel panic.
In function sctp_assoc_lookup_asconf_ack(), if the cached ASCONF-ACKs
list asconf_ack_list is empty, or if the serial being requested does not
exists, the function as it currectly stands returns the actuall
list_head asoc->asconf_ack_list, this is not a cache ASCONF-ACK chunk
but a bogus pointer.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index 13931a91f667..d29f792e0529 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -1525,7 +1525,7 @@ struct sctp_chunk *sctp_assoc_lookup_asconf_ack(
                                         const struct sctp_association *asoc,
                                         __be32 serial)
 {
-        struct sctp_chunk *ack = NULL;
+        struct sctp_chunk *ack;
 
         /* Walk through the list of cached ASCONF-ACKs and find the
          * ack chunk whose serial number matches that of the request.
@@ -1533,9 +1533,9 @@ struct sctp_chunk *sctp_assoc_lookup_asconf_ack(
         list_for_each_entry(ack, &asoc->asconf_ack_list, transmitted_list) {
                 if (ack->subh.addip_hdr->serial == serial) {
                         sctp_chunk_hold(ack);
-                        break;
+                        return ack;
                 }
         }
 
-        return ack;
+        return NULL;
 }