relayd: introduce --working-directory/-w options

This new option allows the user to specify the working directory (CWD) of the
lttng-relayd process. This is especially useful when lttng-relayd is
started in daemon mode (-d) because by default the CWD is set to "/".
This can help control where coredumps, if any, get generated.

Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/bin/lttng-relayd/main.c b/src/bin/lttng-relayd/main.c
index 2836c489ce9647325dc5a8da7d25d18ba0c684b1..ad97a0b9b9871e395ed055860b853b93f55b5e78 100644 (file)
--- a/src/bin/lttng-relayd/main.c
+++ b/src/bin/lttng-relayd/main.c
@@ -96,7 +96,7 @@ enum relay_connection_status {
 };
 
 /* command line options */
-char *opt_output_path;
+char *opt_output_path, *opt_working_directory;
 static int opt_daemon, opt_background, opt_print_version;
 
 /*
@@ -184,6 +184,7 @@ static struct option long_options[] = {
        { "verbose", 0, 0, 'v', },
        { "config", 1, 0, 'f' },
        { "version", 0, 0, 'V' },
+       { "working-directory", 1, 0, 'w', },
        { NULL, 0, 0, 0, },
 };
 
@@ -311,6 +312,20 @@ static int set_option(int opt, const char *arg, const char *optname)
                        }
                }
                break;
+       case 'w':
+               if (lttng_is_setuid_setgid()) {
+                       WARN("Getting '%s' argument from setuid/setgid binary refused for security reasons.",
+                               "-w, --working-directory");
+               } else {
+                       ret = asprintf(&opt_working_directory, "%s", arg);
+                       if (ret < 0) {
+                               ret = -errno;
+                               PERROR("asprintf opt_working_directory");
+                               goto end;
+                       }
+               }
+               break;
+
        case 'v':
                /* Verbose level can increase using multiple -v */
                if (arg) {
@@ -541,8 +556,8 @@ static void relayd_cleanup(void)
        if (sessions_ht)
                lttng_ht_destroy(sessions_ht);
 
-       /* free the dynamically allocated opt_output_path */
        free(opt_output_path);
+       free(opt_working_directory);
 
        /* Close thread quit pipes */
        utils_close_pipe(thread_quit_pipe);
@@ -3729,6 +3744,14 @@ int main(int argc, char **argv)
                }
        }
 
+       if (opt_working_directory) {
+               ret = utils_change_working_directory(opt_working_directory);
+               if (ret) {
+                       /* All errors are already logged. */
+                       goto exit_options;
+               }
+       }
+
        sessiond_trace_chunk_registry = sessiond_trace_chunk_registry_create();
        if (!sessiond_trace_chunk_registry) {
                ERR("Failed to initialize session daemon trace chunk registry");

diff --git a/src/common/utils.c b/src/common/utils.c
index 3cdb6b76063caf4545761a93b52523dd2c39b14c..0147c8c994d3cb89f7fa936633863e043cdd2221 100644 (file)
--- a/src/common/utils.c
+++ b/src/common/utils.c
@@ -1501,3 +1501,35 @@ int utils_get_memory_total(size_t *value)
 {
        return read_proc_meminfo_field(PROC_MEMINFO_MEMTOTAL_LINE, value);
 }
+
+LTTNG_HIDDEN
+int utils_change_working_directory(const char *path)
+{
+       int ret;
+
+       assert(path);
+
+       DBG("Changing working directory to \"%s\"", path);
+       ret = chdir(path);
+       if (ret) {
+               PERROR("Failed to change working directory to \"%s\"", path);
+               goto end;
+       }
+
+       /* Check for write access */
+       if (access(path, W_OK)) {
+               if (errno == EACCES) {
+                       /*
+                        * Do not treat this as an error since the permission
+                        * might change in the lifetime of the process
+                        */
+                       DBG("Working directory \"%s\" is not writable", path);
+               } else {
+                       PERROR("Failed to check if working directory \"%s\" is writable",
+                                       path);
+               }
+       }
+
+end:
+       return ret;
+}

diff --git a/src/common/utils.h b/src/common/utils.h
index 11388c9031bfdaabffd9b1dad596410af43e5e9f..27a6f4849aced6cac50ea2e9ce7e4b0e36ee1693 100644 (file)
--- a/src/common/utils.h
+++ b/src/common/utils.h
@@ -63,5 +63,6 @@ int utils_truncate_stream_file(int fd, off_t length);
 int utils_show_help(int section, const char *page_name, const char *help_msg);
 int utils_get_memory_available(size_t *value);
 int utils_get_memory_total(size_t *value);
+int utils_change_working_directory(const char *path);
 
 #endif /* _COMMON_UTILS_H */