Validate channel context mismatch across UST applications

Observed issue
==============

Applications traced with LTTng-UST are expected to all provide the exact
same layout for their channel's context fields, else it leads to
corrupted traces. This is only enforced within LTTng-UST. There is
nothing in the session daemon that prevents this scenario, and it is
only observable when reading the corrupted trace.

This makes the entire trace unreadable from the point where it is
corrupted.

Cause
=====

Even though LTTng-UST sends the entire description of its context fields
along with the channel registration notification, there is no validation
of the context fields' content against the context fields present in the
ust registry.

Solution
========

Validate each registered UST channel context fields against the fields
present in the registry. Reject the application if there is a mismatch.

Known drawbacks
===============

None.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I8b49032bf4f766e549dfccfafdce8cddcbb2873f

diff --git a/src/bin/lttng-sessiond/ust-app.cpp b/src/bin/lttng-sessiond/ust-app.cpp
index 712e577091975dd97bbae4971d79f6005728168b..54cd4dea645b7e1b30edf06822156bdc3781ed37 100644 (file)
--- a/src/bin/lttng-sessiond/ust-app.cpp
+++ b/src/bin/lttng-sessiond/ust-app.cpp
@@ -49,7 +49,7 @@
 #include "rotate.h"
 #include "event.h"
 #include "event-notifier-error-accounting.h"
-
+#include "ust-field-utils.h"
 
 struct lttng_ht *ust_app_ht;
 struct lttng_ht *ust_app_ht_by_sock;
@@ -6386,6 +6386,9 @@ static int reply_ust_register_channel(int sock, int cobjd,
        ust_reg_chan = ust_registry_channel_find(registry, chan_reg_key);
        LTTNG_ASSERT(ust_reg_chan);
 
+       /* Channel id is set during the object creation. */
+       chan_id = ust_reg_chan->chan_id;
+
        if (!ust_reg_chan->register_done) {
                /*
                 * TODO: eventually use the registry event count for
@@ -6400,9 +6403,19 @@ static int reply_ust_register_channel(int sock, int cobjd,
        } else {
                /* Get current already assigned values. */
                type = ust_reg_chan->header_type;
+               /*
+                * Validate that the context fields match between
+                * registry and newcoming application.
+                */
+               if (!match_lttng_ust_ctl_field_array(ust_reg_chan->ctx_fields,
+                               ust_reg_chan->nr_ctx_fields,
+                               fields, nr_fields)) {
+                       ERR("Registering application channel due to context field mismatch: pid = %d, sock = %d",
+                               app->pid, app->sock);
+                       ret_code = -EINVAL;
+                       goto reply;
+               }
        }
-       /* Channel id is set during the object creation. */
-       chan_id = ust_reg_chan->chan_id;
 
        /* Append to metadata */
        if (!ust_reg_chan->metadata_dumped) {

diff --git a/src/bin/lttng-sessiond/ust-field-utils.cpp b/src/bin/lttng-sessiond/ust-field-utils.cpp
index a89fade5ec93254c237a73a0d45e991e7a5e947e..a8f3da2ba7a96c088d54f373962e56311033697b 100644 (file)
--- a/src/bin/lttng-sessiond/ust-field-utils.cpp
+++ b/src/bin/lttng-sessiond/ust-field-utils.cpp
@@ -338,3 +338,33 @@ int match_lttng_ust_ctl_field(const struct lttng_ust_ctl_field *first,
 no_match:
        return false;
 }
+
+/*
+ * Compare two arrays of UST fields.
+ * Return true if both arrays have identical field definitions, false otherwise.
+ */
+bool match_lttng_ust_ctl_field_array(const struct lttng_ust_ctl_field *first,
+               size_t nr_first,
+               const struct lttng_ust_ctl_field *second,
+               size_t nr_second)
+{
+       size_t i;
+       const size_t nr_fields = nr_first;
+
+       /* Compare the array lengths. */
+       if (nr_first != nr_second) {
+               goto no_match;
+       }
+
+       /* Compare each field individually. */
+       for (i = 0; i < nr_fields; i++) {
+               if (!match_lttng_ust_ctl_field(&first[i], &second[i])) {
+                       goto no_match;
+               }
+       }
+
+       return true;
+
+no_match:
+       return false;
+}

diff --git a/src/bin/lttng-sessiond/ust-field-utils.h b/src/bin/lttng-sessiond/ust-field-utils.h
index ea629d5d5deac91869798ec1cd573585f1b987d3..39cd50b481124f260dae7da9dec5b2a231746501 100644 (file)
--- a/src/bin/lttng-sessiond/ust-field-utils.h
+++ b/src/bin/lttng-sessiond/ust-field-utils.h
@@ -17,4 +17,13 @@
 int match_lttng_ust_ctl_field(const struct lttng_ust_ctl_field *first,
                const struct lttng_ust_ctl_field *second);
 
+/*
+ * Compare two arrays of UST fields.
+ * Return true if both arrays have identical field definitions, false otherwise.
+ */
+bool match_lttng_ust_ctl_field_array(const struct lttng_ust_ctl_field *first,
+               size_t nr_first,
+               const struct lttng_ust_ctl_field *second,
+               size_t nr_second);
+
 #endif /* LTTNG_UST_FIELD_UTILS_H */

diff --git a/src/bin/lttng-sessiond/ust-registry.cpp b/src/bin/lttng-sessiond/ust-registry.cpp
index 17346520380b1d67673fd0dfc10c1fc7cf50e704..088e8d64fedfd36e6aa7cba44ecdc74e68df553a 100644 (file)
--- a/src/bin/lttng-sessiond/ust-registry.cpp
+++ b/src/bin/lttng-sessiond/ust-registry.cpp
@@ -19,7 +19,6 @@
 #include "lttng-sessiond.h"
 #include "notification-thread-commands.h"
 
-
 /*
  * Hash table match function for event in the registry.
  */
@@ -27,7 +26,6 @@ static int ht_match_event(struct cds_lfht_node *node, const void *_key)
 {
        const struct ust_registry_event *key;
        struct ust_registry_event *event;
-       int i;
 
        LTTNG_ASSERT(node);
        LTTNG_ASSERT(_key);
@@ -46,18 +44,12 @@ static int ht_match_event(struct cds_lfht_node *node, const void *_key)
                goto no_match;
        }
 
-       /* Compare the number of fields. */
-       if (event->nr_fields != key->nr_fields) {
+       /* Compare the arrays of fields. */
+       if (!match_lttng_ust_ctl_field_array(event->fields, event->nr_fields,
+                       key->fields, key->nr_fields)) {
                goto no_match;
        }
 
-       /* Compare each field individually. */
-       for (i = 0; i < event->nr_fields; i++) {
-               if (!match_lttng_ust_ctl_field(&event->fields[i], &key->fields[i])) {
-                       goto no_match;
-               }
-       }
-
        /* Compare model URI. */
        if (event->model_emf_uri != NULL && key->model_emf_uri == NULL) {
                goto no_match;