1 files changed, 57 insertions, 5 deletions

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 0fd5b4c88358..30c1767186b8 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -108,7 +108,7 @@ static const struct sctp_paramhdr prsctp_param = {
         cpu_to_be16(sizeof(struct sctp_paramhdr)),
 };
 
-/* A helper to initialize to initialize an op error inside a
+/* A helper to initialize an op error inside a
  * provided chunk, as most cause codes will be embedded inside an
  * abort chunk.
  */
@@ -125,6 +125,29 @@ void  sctp_init_cause(struct sctp_chunk *chunk, __be16 cause_code,
         chunk->subh.err_hdr = sctp_addto_chunk(chunk, sizeof(sctp_errhdr_t), &err);
 }
 
+/* A helper to initialize an op error inside a
+ * provided chunk, as most cause codes will be embedded inside an
+ * abort chunk.  Differs from sctp_init_cause in that it won't oops
+ * if there isn't enough space in the op error chunk
+ */
+int sctp_init_cause_fixed(struct sctp_chunk *chunk, __be16 cause_code,
+                      size_t paylen)
+{
+        sctp_errhdr_t err;
+        __u16 len;
+
+        /* Cause code constants are now defined in network order.  */
+        err.cause = cause_code;
+        len = sizeof(sctp_errhdr_t) + paylen;
+        err.length  = htons(len);
+
+        if (skb_tailroom(chunk->skb) >  len)
+                return -ENOSPC;
+        chunk->subh.err_hdr = sctp_addto_chunk_fixed(chunk,
+                                                     sizeof(sctp_errhdr_t),
+                                                     &err);
+        return 0;
+}
 /* 3.3.2 Initiation (INIT) (1)
  *
  * This chunk is used to initiate a SCTP association between two
@@ -1132,6 +1155,24 @@ nodata:
         return retval;
 }
 
+/* Create an Operation Error chunk of a fixed size,
+ * specifically, max(asoc->pathmtu, SCTP_DEFAULT_MAXSEGMENT)
+ * This is a helper function to allocate an error chunk for
+ * for those invalid parameter codes in which we may not want
+ * to report all the errors, if the incomming chunk is large
+ */
+static inline struct sctp_chunk *sctp_make_op_error_fixed(
+        const struct sctp_association *asoc,
+        const struct sctp_chunk *chunk)
+{
+        size_t size = asoc ? asoc->pathmtu : 0;
+
+        if (!size)
+                size = SCTP_DEFAULT_MAXSEGMENT;
+
+        return sctp_make_op_error_space(asoc, chunk, size);
+}
+
 /* Create an Operation Error chunk.  */
 struct sctp_chunk *sctp_make_op_error(const struct sctp_association *asoc,
                                  const struct sctp_chunk *chunk,
@@ -1374,6 +1415,18 @@ void *sctp_addto_chunk(struct sctp_chunk *chunk, int len, const void *data)
         return target;
 }
 
+/* Append bytes to the end of a chunk. Returns NULL if there isn't sufficient
+ * space in the chunk
+ */
+void *sctp_addto_chunk_fixed(struct sctp_chunk *chunk,
+                             int len, const void *data)
+{
+        if (skb_tailroom(chunk->skb) > len)
+                return sctp_addto_chunk(chunk, len, data);
+        else
+                return NULL;
+}
+
 /* Append bytes from user space to the end of a chunk.  Will panic if
  * chunk is not big enough.
  * Returns a kernel err value.
@@ -1977,13 +2030,12 @@ static sctp_ierror_t sctp_process_unk_param(const struct sctp_association *asoc,
                  * returning multiple unknown parameters.
                  */
                 if (NULL == *errp)
-                        *errp = sctp_make_op_error_space(asoc, chunk,
-                                        ntohs(chunk->chunk_hdr->length));
+                        *errp = sctp_make_op_error_fixed(asoc, chunk);
 
                 if (*errp) {
-                        sctp_init_cause(*errp, SCTP_ERROR_UNKNOWN_PARAM,
+                        sctp_init_cause_fixed(*errp, SCTP_ERROR_UNKNOWN_PARAM,
                                         WORD_ROUND(ntohs(param.p->length)));
-                        sctp_addto_chunk(*errp,
+                        sctp_addto_chunk_fixed(*errp,
                                         WORD_ROUND(ntohs(param.p->length)),
                                         param.v);
                 } else {