Use dynamic buffer to build session configuration path

Re-use the dynamic buffer interface to build the session
configuration path. The main benefit here is silencing a source
string truncation warning emitted by GCC 8. However, this
interface is also simpler to use than manually building the
path.

The LTTNG_PATH_MAX is still enforced, but there is no real
need to restrict paths to that size. This could be removed if
it ever poses a problem.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/common/config/session-config.c b/src/common/config/session-config.c
index a600a5b47fe72b1dcec9f807a73f2ef899ace7df..624064a107ef6851e7a2a4820b4ce858722a9c63 100644 (file)
--- a/src/common/config/session-config.c
+++ b/src/common/config/session-config.c
@@ -32,6 +32,7 @@
 #include <common/error.h>
 #include <common/macros.h>
 #include <common/utils.h>
+#include <common/dynamic-buffer.h>
 #include <common/compat/getenv.h>
 #include <lttng/lttng-error.h>
 #include <libxml/parser.h>
@@ -2976,9 +2977,19 @@ int load_session_from_path(const char *path, const char *session_name,
 {
        int ret, session_found = !session_name;
        DIR *directory = NULL;
+       struct lttng_dynamic_buffer file_path;
+       size_t path_len;
 
        assert(path);
        assert(validation_ctx);
+       path_len = strlen(path);
+       lttng_dynamic_buffer_init(&file_path);
+       if (path_len >= LTTNG_PATH_MAX) {
+               ERR("Session configuration load path \"%s\" length (%zu) exceeds the maximal length allowed (%d)",
+                               path, path_len, LTTNG_PATH_MAX);
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
 
        directory = opendir(path);
        if (!directory) {
@@ -2997,11 +3008,12 @@ int load_session_from_path(const char *path, const char *session_name,
        if (directory) {
                struct dirent *entry;
                struct dirent *result;
-               char *file_path = NULL;
-               size_t path_len = strlen(path);
+               size_t file_path_root_len;
 
-               if (path_len >= PATH_MAX) {
-                       ret = -LTTNG_ERR_INVALID;
+               ret = lttng_dynamic_buffer_set_capacity(&file_path,
+                               LTTNG_PATH_MAX);
+               if (ret) {
+                       ret = -LTTNG_ERR_NOMEM;
                        goto end;
                }
 
@@ -3011,19 +3023,22 @@ int load_session_from_path(const char *path, const char *session_name,
                        goto end;
                }
 
-               file_path = zmalloc(PATH_MAX);
-               if (!file_path) {
+               ret = lttng_dynamic_buffer_append(&file_path, path, path_len);
+               if (ret) {
                        ret = -LTTNG_ERR_NOMEM;
                        free(entry);
                        goto end;
                }
 
-               strncpy(file_path, path, path_len);
-               if (file_path[path_len - 1] != '/') {
-                       file_path[path_len++] = '/';
+               if (file_path.data[file_path.size - 1] != '/') {
+                       ret = lttng_dynamic_buffer_append(&file_path, "/", 1);
+                       if (ret) {
+                               ret = -LTTNG_ERR_NOMEM;
+                               goto end;
+                       }
                }
+               file_path_root_len = file_path.size;
 
-               ret = 0;
                /* Search for *.lttng files */
                while (!readdir_r(directory, entry, &result) && result) {
                        size_t file_name_len = strlen(result->d_name);
@@ -3033,29 +3048,48 @@ int load_session_from_path(const char *path, const char *session_name,
                                continue;
                        }
 
-                       if (path_len + file_name_len >= PATH_MAX) {
+                       if (file_path.size + file_name_len >= LTTNG_PATH_MAX) {
+                               WARN("Ignoring file \"%s\" since the path's length (%zu) would exceed the maximal permitted size (%d)",
+                                               result->d_name,
+                                               /* +1 to account for NULL terminator. */
+                                               file_path.size + file_name_len + 1,
+                                               LTTNG_PATH_MAX);
                                continue;
                        }
 
+                       /* Does the file end with .lttng? */
                        if (strcmp(DEFAULT_SESSION_CONFIG_FILE_EXTENSION,
-                               result->d_name + file_name_len - sizeof(
-                               DEFAULT_SESSION_CONFIG_FILE_EXTENSION) + 1)) {
+                                       result->d_name + file_name_len - sizeof(
+                                       DEFAULT_SESSION_CONFIG_FILE_EXTENSION) + 1)) {
                                continue;
                        }
 
-                       strncpy(file_path + path_len, result->d_name, file_name_len);
-                       file_path[path_len + file_name_len] = '\0';
+                       ret = lttng_dynamic_buffer_append(&file_path, result->d_name,
+                                       file_name_len + 1);
+                       if (ret) {
+                               ret = -LTTNG_ERR_NOMEM;
+                               goto end;
+                       }
 
-                       ret = load_session_from_file(file_path, session_name,
+                       ret = load_session_from_file(file_path.data, session_name,
                                validation_ctx, overwrite, overrides);
                        if (session_name && !ret) {
                                session_found = 1;
                                break;
                        }
+                       /*
+                        * Reset the buffer's size to the location of the
+                        * path's trailing '/'.
+                        */
+                       ret = lttng_dynamic_buffer_set_size(&file_path,
+                                       file_path_root_len);
+                       if (ret) {
+                               ret = -LTTNG_ERR_UNK;
+                               goto end;
+                       }
                }
 
                free(entry);
-               free(file_path);
        } else {
                ret = load_session_from_file(path, session_name,
                        validation_ctx, overwrite, overrides);
@@ -3072,11 +3106,10 @@ end:
                        PERROR("closedir");
                }
        }
-
        if (session_found && !ret) {
                ret = 0;
        }
-
+       lttng_dynamic_buffer_reset(&file_path);
        return ret;
 }