Merge branch 'bug18570_027' into maint-0.2.7

changes/bug18570

@@ -0,0 +1,7 @@
+  o Minor bugfixes (correctness):
+    - Fix a bad memory handling bug that would occur if we had queued
+      a cell on a channel's incoming queue. Fortunately, we can't actually
+      queue a cell like that as our code is constructed today, but it's best
+      to avoid this kind of error, even if there isn't any code that triggers
+      it today. Fixes bug 18570; bugfix on 0.2.4.4-alpha.
+

src/or/channel.c

@@ -2652,6 +2652,11 @@ channel_process_cells(channel_t *chan)
   /*
    * Process cells until we're done or find one we have no current handler
    * for.
+   *
+   * We must free the cells here after calling the handler, since custody
+   * of the buffer was given to the channel layer when they were queued;
+   * see comments on memory management in channel_queue_cell() and in
+   * channel_queue_var_cell() below.
    */
   while (NULL != (q = TOR_SIMPLEQ_FIRST(&chan->incoming_queue))) {
     tor_assert(q);
@@ -2669,6 +2674,7 @@ channel_process_cells(channel_t *chan)
                 q->u.fixed.cell, chan,
                 U64_PRINTF_ARG(chan->global_identifier));
       chan->cell_handler(chan, q->u.fixed.cell);
+      tor_free(q->u.fixed.cell);
       tor_free(q);
     } else if (q->type == CELL_QUEUE_VAR &&
                chan->var_cell_handler) {
@@ -2681,6 +2687,7 @@ channel_process_cells(channel_t *chan)
                 q->u.var.var_cell, chan,
                 U64_PRINTF_ARG(chan->global_identifier));
       chan->var_cell_handler(chan, q->u.var.var_cell);
+      tor_free(q->u.var.var_cell);
       tor_free(q);
     } else {
       /* Can't handle this one */
@@ -2701,6 +2708,7 @@ channel_queue_cell(channel_t *chan, cell_t *cell)
 {
   int need_to_queue = 0;
   cell_queue_entry_t *q;
+  cell_t *cell_copy = NULL;
 
   tor_assert(chan);
   tor_assert(cell);
@@ -2728,8 +2736,19 @@ channel_queue_cell(channel_t *chan, cell_t *cell)
               U64_PRINTF_ARG(chan->global_identifier));
     chan->cell_handler(chan, cell);
   } else {
-    /* Otherwise queue it and then process the queue if possible. */
-    q = cell_queue_entry_new_fixed(cell);
+    /*
+     * Otherwise queue it and then process the queue if possible.
+     *
+     * We queue a copy, not the original pointer - it might have been on the
+     * stack in connection_or_process_cells_from_inbuf() (or another caller
+     * if we ever have a subclass other than channel_tls_t), or be freed
+     * there after we return.  This is the uncommon case; the non-copying
+     * fast path occurs in the if (!need_to_queue) case above when the
+     * upper layer has installed cell handlers.
+     */
+    cell_copy = tor_malloc_zero(sizeof(cell_t));
+    memcpy(cell_copy, cell, sizeof(cell_t));
+    q = cell_queue_entry_new_fixed(cell_copy);
     log_debug(LD_CHANNEL,
               "Queueing incoming cell_t %p for channel %p "
               "(global ID " U64_FORMAT ")",
@@ -2755,6 +2774,7 @@ channel_queue_var_cell(channel_t *chan, var_cell_t *var_cell)
 {
   int need_to_queue = 0;
   cell_queue_entry_t *q;
+  var_cell_t *cell_copy = NULL;
 
   tor_assert(chan);
   tor_assert(var_cell);
@@ -2783,8 +2803,18 @@ channel_queue_var_cell(channel_t *chan, var_cell_t *var_cell)
               U64_PRINTF_ARG(chan->global_identifier));
     chan->var_cell_handler(chan, var_cell);
   } else {
-    /* Otherwise queue it and then process the queue if possible. */
-    q = cell_queue_entry_new_var(var_cell);
+    /*
+     * Otherwise queue it and then process the queue if possible.
+     *
+     * We queue a copy, not the original pointer - it might have been on the
+     * stack in connection_or_process_cells_from_inbuf() (or another caller
+     * if we ever have a subclass other than channel_tls_t), or be freed
+     * there after we return.  This is the uncommon case; the non-copying
+     * fast path occurs in the if (!need_to_queue) case above when the
+     * upper layer has installed cell handlers.
+     */
+    cell_copy = var_cell_copy(var_cell);
+    q = cell_queue_entry_new_var(cell_copy);
     log_debug(LD_CHANNEL,
               "Queueing incoming var_cell_t %p for channel %p "
               "(global ID " U64_FORMAT ")",

src/or/channeltls.c

@@ -1009,6 +1009,11 @@ channel_tls_time_process_cell(cell_t *cell, channel_tls_t *chan, int *time,
  * for cell types specific to the handshake for this transport protocol and
  * handles them, and queues all other cells to the channel_t layer, which
  * eventually will hand them off to command.c.
+ *
+ * The channel layer itself decides whether the cell should be queued or
+ * can be handed off immediately to the upper-layer code.  It is responsible
+ * for copying in the case that it queues; we merely pass pointers through
+ * which we get from connection_or_process_cells_from_inbuf().
  */
 
 void
@@ -1106,6 +1111,12 @@ channel_tls_handle_cell(cell_t *cell, or_connection_t *conn)
  * related and live below the channel_t layer, so no variable-length
  * cells ever get delivered in the current implementation, but I've left
  * the mechanism in place for future use.
+ *
+ * If we were handing them off to the upper layer, the channel_t queueing
+ * code would be responsible for memory management, and we'd just be passing
+ * pointers through from connection_or_process_cells_from_inbuf().  That
+ * caller always frees them after this function returns, so this function
+ * should never free var_cell.
  */
 
 void

src/or/connection_or.c

@@ -488,6 +488,28 @@ var_cell_new(uint16_t payload_len)
   return cell;
 }
 
+/**
+ * Copy a var_cell_t
+ */
+
+var_cell_t *
+var_cell_copy(const var_cell_t *src)
+{
+  var_cell_t *copy = NULL;
+  size_t size = 0;
+
+  if (src != NULL) {
+    size = STRUCT_OFFSET(var_cell_t, payload) + src->payload_len;
+    copy = tor_malloc_zero(size);
+    copy->payload_len = src->payload_len;
+    copy->command = src->command;
+    copy->circ_id = src->circ_id;
+    memcpy(copy->payload, src->payload, copy->payload_len);
+  }
+
+  return copy;
+}
+
 /** Release all space held by <b>cell</b>. */
 void
 var_cell_free(var_cell_t *cell)
@@ -2060,6 +2082,19 @@ connection_or_process_cells_from_inbuf(or_connection_t *conn)
 {
   var_cell_t *var_cell;
 
+  /*
+   * Note on memory management for incoming cells: below the channel layer,
+   * we shouldn't need to consider its internal queueing/copying logic.  It
+   * is safe to pass cells to it on the stack or on the heap, but in the
+   * latter case we must be sure we free them later.
+   *
+   * The incoming cell queue code in channel.c will (in the common case)
+   * decide it can pass them to the upper layer immediately, in which case
+   * those functions may run directly on the cell pointers we pass here, or
+   * it may decide to queue them, in which case it will allocate its own
+   * buffer and copy the cell.
+   */
+
   while (1) {
     log_debug(LD_OR,
               TOR_SOCKET_T_FORMAT": starting, inbuf_datalen %d "

src/or/connection_or.h

@@ -97,6 +97,7 @@ void cell_pack(packed_cell_t *dest, const cell_t *src, int wide_circ_ids);
 int var_cell_pack_header(const var_cell_t *cell, char *hdr_out,
                          int wide_circ_ids);
 var_cell_t *var_cell_new(uint16_t payload_len);
+var_cell_t *var_cell_copy(const var_cell_t *src);
 void var_cell_free(var_cell_t *cell);
 
 /** DOCDOC */

src/test/test_channel.c

@@ -25,7 +25,9 @@ extern uint64_t estimated_total_queue_size;
 
 static int test_chan_accept_cells = 0;
 static int test_chan_fixed_cells_recved = 0;
+static cell_t * test_chan_last_seen_fixed_cell_ptr = NULL;
 static int test_chan_var_cells_recved = 0;
+static var_cell_t * test_chan_last_seen_var_cell_ptr = NULL;
 static int test_cells_written = 0;
 static int test_destroy_not_pending_calls = 0;
 static int test_doesnt_want_writes_count = 0;
@@ -70,6 +72,7 @@ static void test_channel_flushmux(void *arg);
 static void test_channel_incoming(void *arg);
 static void test_channel_lifecycle(void *arg);
 static void test_channel_multi(void *arg);
+static void test_channel_queue_incoming(void *arg);
 static void test_channel_queue_size(void *arg);
 static void test_channel_write(void *arg);
 
@@ -179,7 +182,7 @@ chan_test_cell_handler(channel_t *ch,
   tt_assert(ch);
   tt_assert(cell);
 
-  tor_free(cell);
+  test_chan_last_seen_fixed_cell_ptr = cell;
   ++test_chan_fixed_cells_recved;
 
  done:
@@ -214,7 +217,7 @@ chan_test_var_cell_handler(channel_t *ch,
   tt_assert(ch);
   tt_assert(var_cell);
 
-  tor_free(var_cell);
+  test_chan_last_seen_var_cell_ptr = var_cell;
   ++test_chan_var_cells_recved;
 
  done:
@@ -608,7 +611,7 @@ test_channel_dumpstats(void *arg)
   make_fake_cell(cell);
   old_count = test_chan_fixed_cells_recved;
   channel_queue_cell(ch, cell);
-  cell = NULL;
+  tor_free(cell);
   tt_int_op(test_chan_fixed_cells_recved, ==, old_count + 1);
   tt_assert(ch->n_bytes_recved > 0);
   tt_assert(ch->n_cells_recved > 0);
@@ -819,7 +822,7 @@ test_channel_incoming(void *arg)
   make_fake_cell(cell);
   old_count = test_chan_fixed_cells_recved;
   channel_queue_cell(ch, cell);
-  cell = NULL;
+  tor_free(cell);
   tt_int_op(test_chan_fixed_cells_recved, ==, old_count + 1);
 
   /* Receive a variable-size cell */
@@ -827,7 +830,7 @@ test_channel_incoming(void *arg)
   make_fake_var_cell(var_cell);
   old_count = test_chan_var_cells_recved;
   channel_queue_var_cell(ch, var_cell);
-  var_cell = NULL;
+  tor_free(cell);
   tt_int_op(test_chan_var_cells_recved, ==, old_count + 1);
 
   /* Close it */
@@ -1422,6 +1425,113 @@ test_channel_queue_impossible(void *arg)
   return;
 }
 
+static void
+test_channel_queue_incoming(void *arg)
+{
+  channel_t *ch = NULL;
+  cell_t *cell = NULL;
+  var_cell_t *var_cell = NULL;
+  int old_fixed_count, old_var_count;
+
+  (void)arg;
+
+  /* Mock these for duration of the test */
+  MOCK(scheduler_channel_doesnt_want_writes,
+       scheduler_channel_doesnt_want_writes_mock);
+  MOCK(scheduler_release_channel,
+       scheduler_release_channel_mock);
+
+  /* Accept cells to lower layer */
+  test_chan_accept_cells = 1;
+  /* Use default overhead factor */
+  test_overhead_estimate = 1.0f;
+
+  ch = new_fake_channel();
+  tt_assert(ch);
+  /* Start it off in OPENING */
+  ch->state = CHANNEL_STATE_OPENING;
+  /* We'll need a cmux */
+  ch->cmux = circuitmux_alloc();
+
+  /* Test cell handler getters */
+  tt_ptr_op(channel_get_cell_handler(ch), ==, NULL);
+  tt_ptr_op(channel_get_var_cell_handler(ch), ==, NULL);
+
+  /* Try to register it */
+  channel_register(ch);
+  tt_assert(ch->registered);
+
+  /* Open it */
+  channel_change_state(ch, CHANNEL_STATE_OPEN);
+  tt_int_op(ch->state, ==, CHANNEL_STATE_OPEN);
+
+  /* Assert that the incoming queue is empty */
+  tt_assert(TOR_SIMPLEQ_EMPTY(&(ch->incoming_queue)));
+
+  /* Queue an incoming fixed-length cell */
+  cell = tor_malloc_zero(sizeof(cell_t));
+  make_fake_cell(cell);
+  channel_queue_cell(ch, cell);
+
+  /* Assert that the incoming queue has one entry */
+  tt_int_op(chan_cell_queue_len(&(ch->incoming_queue)), ==, 1);
+
+  /* Queue an incoming var cell */
+  var_cell = tor_malloc_zero(sizeof(var_cell_t) + CELL_PAYLOAD_SIZE);
+  make_fake_var_cell(var_cell);
+  channel_queue_var_cell(ch, var_cell);
+
+  /* Assert that the incoming queue has two entries */
+  tt_int_op(chan_cell_queue_len(&(ch->incoming_queue)), ==, 2);
+
+  /*
+   * Install cell handlers; this will drain the queue, so save the old
+   * cell counters first
+   */
+  old_fixed_count = test_chan_fixed_cells_recved;
+  old_var_count = test_chan_var_cells_recved;
+  channel_set_cell_handlers(ch,
+                            chan_test_cell_handler,
+                            chan_test_var_cell_handler);
+  tt_ptr_op(channel_get_cell_handler(ch), ==, chan_test_cell_handler);
+  tt_ptr_op(channel_get_var_cell_handler(ch), ==, chan_test_var_cell_handler);
+
+  /* Assert cells were received */
+  tt_int_op(test_chan_fixed_cells_recved, ==, old_fixed_count + 1);
+  tt_int_op(test_chan_var_cells_recved, ==, old_var_count + 1);
+
+  /*
+   * Assert that the pointers are different from the cells we allocated;
+   * when queueing cells with no incoming cell handlers installed, the
+   * channel layer should copy them to a new buffer, and free them after
+   * delivery.  These pointers will have already been freed by the time
+   * we get here, so don't dereference them.
+   */
+  tt_ptr_op(test_chan_last_seen_fixed_cell_ptr, !=, cell);
+  tt_ptr_op(test_chan_last_seen_var_cell_ptr, !=, var_cell);
+
+  /* Assert queue is now empty */
+  tt_assert(TOR_SIMPLEQ_EMPTY(&(ch->incoming_queue)));
+
+  /* Close it; this contains an assertion that the incoming queue is empty */
+  channel_mark_for_close(ch);
+  tt_int_op(ch->state, ==, CHANNEL_STATE_CLOSING);
+  chan_test_finish_close(ch);
+  tt_int_op(ch->state, ==, CHANNEL_STATE_CLOSED);
+  channel_run_cleanup();
+  ch = NULL;
+
+ done:
+  free_fake_channel(ch);
+  tor_free(cell);
+  tor_free(var_cell);
+
+  UNMOCK(scheduler_channel_doesnt_want_writes);
+  UNMOCK(scheduler_release_channel);
+
+  return;
+}
+
 static void
 test_channel_queue_size(void *arg)
 {
@@ -1666,6 +1776,7 @@ struct testcase_t channel_tests[] = {
   { "lifecycle_2", test_channel_lifecycle_2, TT_FORK, NULL, NULL },
   { "multi", test_channel_multi, TT_FORK, NULL, NULL },
   { "queue_impossible", test_channel_queue_impossible, TT_FORK, NULL, NULL },
+  { "queue_incoming", test_channel_queue_incoming, TT_FORK, NULL, NULL },
   { "queue_size", test_channel_queue_size, TT_FORK, NULL, NULL },
   { "write", test_channel_write, TT_FORK, NULL, NULL },
   END_OF_TESTCASES