AST-2017-004: chan_skinny: Add EOF check in skinny_session

The while(1) loop in skinny_session wasn't checking for EOF so
a packet that was longer than a header but still truncated
would spin the while loop infinitely.  Not only does this
permanently tie up a thread and drive a core to 100% utilization,
the call of ast_log() in such a tight loop eats all available
process memory.

Added poll with timeout to top of read loop

ASTERISK-26940 #close
Reported-by: Sandro Gauci

Change-Id: I2ce65f3c5cb24b4943a9f75b64d545a1e2cd2898

channels/chan_skinny.c

@@ -7502,6 +7502,8 @@ static void skinny_session_cleanup(void *data)
 	destroy_session(s);
 }
 
+#define PACKET_TIMEOUT 10000
+
 static void *skinny_session(void *data)
 {
 	int res;
@@ -7548,7 +7550,10 @@ static void *skinny_session(void *data)
 			}
 		}
 
-		if (fds[0].revents) {
+		if (!fds[0].revents) {
+			continue;
+		}
+		ast_debug(1, "Reading header\n");
 
 		if (!(req = ast_calloc(1, SKINNY_MAX_PACKET))) {
 			ast_log(LOG_WARNING, "Unable to allocated memorey for skinny_req.\n");
@@ -7583,30 +7588,36 @@ static void *skinny_session(void *data)
 			break;
 		}
 
+		ast_debug(1, "Read header: Message ID: 0x%04x,  %d bytes in packet\n", eventmessage, dlen);
+
 		bytesread = 0;
-			while (1) {
-				if ((res = read(s->fd, ((char*)&req->data)+bytesread, dlen-bytesread)) < 0) {
-					ast_log(LOG_WARNING, "Data read() returned error: %s\n", strerror(errno));
-					break;
-				}
-				bytesread += res;
-				if (bytesread >= dlen) {
-					if (res < bytesread) {
-						ast_log(LOG_WARNING, "Rest of partial data received.\n");
+		while (bytesread < dlen) {
+			ast_debug(1, "Waiting %dms for %d bytes of %d\n", PACKET_TIMEOUT, dlen - bytesread, dlen);
+			fds[0].revents = 0;
+			res = ast_poll(fds, 1, PACKET_TIMEOUT);
+			if (res <= 0) {
+				if (res == 0) {
+					ast_debug(1, "Poll timed out waiting for %d bytes\n", dlen - bytesread);
+				} else {
+					ast_log(LOG_WARNING, "Poll failed waiting for %d bytes: %s\n",
+						dlen - bytesread, strerror(errno));
 				}
-					if (bytesread > dlen) {
-						ast_log(LOG_WARNING, "Client sent wrong amount of data (%d), expected (%d).\n", bytesread, dlen);
+				ast_verb(3, "Ending Skinny session from %s (bad input)\n", ast_inet_ntoa(s->sin.sin_addr));
 				res = -1;
-					}
+
 				break;
 			}
+			if (!fds[0].revents) {
+				continue;
+			}
 
-				ast_log(LOG_WARNING, "Partial data received, waiting (%d bytes read of %d)\n", bytesread, dlen);
-				if (sched_yield() < 0) {
-					ast_log(LOG_WARNING, "Data yield() returned error: %s\n", strerror(errno));
-					res = -1;
+			res = read(s->fd, ((char*)&req->data)+bytesread, dlen-bytesread);
+			if (res < 0) {
+				ast_log(LOG_WARNING, "Data read() returned error: %s\n", strerror(errno));
 				break;
 			}
+			bytesread += res;
+			ast_debug(1, "Read %d bytes.  %d of %d now read\n", res, bytesread, dlen);
 		}
 
 		s->lockstate = 0;
@@ -7618,7 +7629,6 @@ static void *skinny_session(void *data)
 		pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);
 		res = handle_message(req, s);
 		pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
-		}
 
 		if (req) {
 			ast_free(req);