sctp: move the format error check out of __sctp_sf_do_9_1_abort

When T2 timer is to be stopped, the asoc should also be deleted,
otherwise, there will be no chance to call sctp_association_free
and the asoc could last in memory forever.

However, in sctp_sf_shutdown_sent_abort(), after adding the cmd
SCTP_CMD_TIMER_STOP for T2 timer, it may return error due to the
format error from __sctp_sf_do_9_1_abort() and miss adding
SCTP_CMD_ASSOC_FAILED where the asoc will be deleted.

This patch is to fix it by moving the format error check out of
__sctp_sf_do_9_1_abort(), and do it before adding the cmd
SCTP_CMD_TIMER_STOP for T2 timer.

Thanks Hangbin for reporting this issue by the fuzz testing.

v1->v2:
  - improve the comment in the code as Marcelo's suggestion.

Fixes: 96ca468b86b0 ("sctp: check invalid value of length parameter in error cause")
Reported-by: Hangbin Liu <liuhangbin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index 748e3b19ec1dc2c7d8ed1dbc83193b7f077c7eb2..6a16af4b1ef61810fed8a04169109f311b070575 100644 (file)
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -170,6 +170,16 @@ static inline bool sctp_chunk_length_valid(struct sctp_chunk *chunk,
        return true;
 }
 
+/* Check for format error in an ABORT chunk */
+static inline bool sctp_err_chunk_valid(struct sctp_chunk *chunk)
+{
+       struct sctp_errhdr *err;
+
+       sctp_walk_errors(err, chunk->chunk_hdr);
+
+       return (void *)err == (void *)chunk->chunk_end;
+}
+
 /**********************************************************
  * These are the state functions for handling chunk events.
  **********************************************************/
@@ -2255,6 +2265,9 @@ enum sctp_disposition sctp_sf_shutdown_pending_abort(
                    sctp_bind_addr_state(&asoc->base.bind_addr, &chunk->dest))
                return sctp_sf_discard_chunk(net, ep, asoc, type, arg, commands);
 
+       if (!sctp_err_chunk_valid(chunk))
+               return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
+
        return __sctp_sf_do_9_1_abort(net, ep, asoc, type, arg, commands);
 }
 
@@ -2298,6 +2311,9 @@ enum sctp_disposition sctp_sf_shutdown_sent_abort(
                    sctp_bind_addr_state(&asoc->base.bind_addr, &chunk->dest))
                return sctp_sf_discard_chunk(net, ep, asoc, type, arg, commands);
 
+       if (!sctp_err_chunk_valid(chunk))
+               return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
+
        /* Stop the T2-shutdown timer. */
        sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
                        SCTP_TO(SCTP_EVENT_TIMEOUT_T2_SHUTDOWN));
@@ -2565,6 +2581,9 @@ enum sctp_disposition sctp_sf_do_9_1_abort(
                    sctp_bind_addr_state(&asoc->base.bind_addr, &chunk->dest))
                return sctp_sf_discard_chunk(net, ep, asoc, type, arg, commands);
 
+       if (!sctp_err_chunk_valid(chunk))
+               return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
+
        return __sctp_sf_do_9_1_abort(net, ep, asoc, type, arg, commands);
 }
 
@@ -2582,16 +2601,8 @@ static enum sctp_disposition __sctp_sf_do_9_1_abort(
 
        /* See if we have an error cause code in the chunk.  */
        len = ntohs(chunk->chunk_hdr->length);
-       if (len >= sizeof(struct sctp_chunkhdr) + sizeof(struct sctp_errhdr)) {
-               struct sctp_errhdr *err;
-
-               sctp_walk_errors(err, chunk->chunk_hdr);
-               if ((void *)err != (void *)chunk->chunk_end)
-                       return sctp_sf_pdiscard(net, ep, asoc, type, arg,
-                                               commands);
-
+       if (len >= sizeof(struct sctp_chunkhdr) + sizeof(struct sctp_errhdr))
                error = ((struct sctp_errhdr *)chunk->skb->data)->cause;
-       }
 
        sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR, SCTP_ERROR(ECONNRESET));
        /* ASSOC_FAILED will DELETE_TCB. */