Wrap unsafe libltdl calls with locking (#848)

* Wrap unsafe libltdl calls with locking

https://github.com/gphoto/libgphoto2/issues/166

* 848: do not install internal header gphoto2-port-mutex.h

* 848: wrap symbol declarations in #ifdef _GPHOTO2_INTERNAL_CODE

* 848: Use proper include guard macro

* 848: Encapsulate the lock/unlock code inside functions

This hides the pthread usage as an implementation detail inside the
gpi_libltdl_lock() and gpi_libltdl_unlock() functions.

* 848: Rename from *-mutex.[ch] to *-locking.[ch]

The *-lock.[ch] name is implementation neutral.

* 848: update libgphoto2_port version number

* 848: internal headers do not require __cplusplus checks

* 848: add copyright comment at the beginning of *.[ch]

* 848: add an unlocked variant of gp_abilities_list_load_dir to avoid lots of unlock/lock codes

* 848: remove unnecessary whitespace addition

Co-authored-by: kadler15 <spurfan15@gmail.com>
Co-authored-by: Hans Ulrich Niedermann <hun@n-dimensional.de>

2 files changed, 33 insertions, 6 deletions

diff --git a/libgphoto2/gphoto2-abilities-list.c b/libgphoto2/gphoto2-abilities-list.c
index b4a9725d1..7db617aed 100644
--- a/libgphoto2/gphoto2-abilities-list.c
+++ b/libgphoto2/gphoto2-abilities-list.c
@@ -36,6 +36,7 @@
 #include <gphoto2/gphoto2-result.h>
 #include <gphoto2/gphoto2-port-log.h>
 #include <gphoto2/gphoto2-library.h>
+#include <gphoto2/gphoto2-port-locking.h>
 
 #include "libgphoto2/i18n.h"
 
@@ -185,9 +186,8 @@ foreach_func (const char *filename, lt_ptr data)
 	return ((fd->result == GP_OK)?0:1);
 }
 
-
-int
-gp_abilities_list_load_dir (CameraAbilitiesList *list, const char *dir,
+static int
+unlocked_gp_abilities_list_load_dir (CameraAbilitiesList *list, const char *dir,
 			    GPContext *context)
 {
 	CameraLibraryIdFunc id;
@@ -295,7 +295,6 @@ gp_abilities_list_load_dir (CameraAbilitiesList *list, const char *dir,
 #if !defined(VALGRIND)
 		lt_dlclose (lh);
 #endif
-
 		new_count = gp_abilities_list_count (list);
 		if (new_count < 0)
 			continue;
@@ -310,16 +309,29 @@ gp_abilities_list_load_dir (CameraAbilitiesList *list, const char *dir,
 		if (gp_context_cancel (context) == GP_CONTEXT_FEEDBACK_CANCEL) {
 			lt_dlexit ();
 			gp_list_free (flist);
-			return (GP_ERROR_CANCEL);
+			return GP_ERROR_CANCEL;
 		}
 	}
 	gp_context_progress_stop (context, p);
 	lt_dlexit ();
 	gp_list_free (flist);
 
-	return (GP_OK);
+	return GP_OK;
 }
 
+int
+gp_abilities_list_load_dir (CameraAbilitiesList *list, const char *dir,
+			    GPContext *context)
+{
+	int ret;
+
+	gpi_libltdl_lock();
+	ret = unlocked_gp_abilities_list_load_dir (list, dir, context);
+	gpi_libltdl_unlock();
+	return ret;
+}
+
+
 
 /**
  * \brief Scans the system for camera drivers.
diff --git a/libgphoto2/gphoto2-camera.c b/libgphoto2/gphoto2-camera.c
index 91828df46..745d7f988 100644
--- a/libgphoto2/gphoto2-camera.c
+++ b/libgphoto2/gphoto2-camera.c
@@ -37,6 +37,7 @@
 #include <gphoto2/gphoto2-result.h>
 #include <gphoto2/gphoto2-library.h>
 #include <gphoto2/gphoto2-port-log.h>
+#include <gphoto2/gphoto2-port-locking.h>
 
 #include "libgphoto2/i18n.h"
 
@@ -279,8 +280,10 @@ gp_camera_exit (Camera *camera, GPContext *context)
 
 	if (camera->pc->lh) {
 #if !defined(VALGRIND)
+		gpi_libltdl_lock();
 		lt_dlclose (camera->pc->lh);
 		lt_dlexit ();
+		gpi_libltdl_unlock();
 #endif
 		camera->pc->lh = NULL;
 	}
@@ -777,21 +780,29 @@ gp_camera_init (Camera *camera, GPContext *context)
 
 	/* Load the library. */
 	GP_LOG_D ("Loading '%s'...", camera->pc->a.library);
+	gpi_libltdl_lock();
 	lt_dlinit ();
 	camera->pc->lh = lt_dlopenext (camera->pc->a.library);
+	gpi_libltdl_unlock();
 	if (!camera->pc->lh) {
+		gpi_libltdl_lock();
 		gp_context_error (context, _("Could not load required "
 			"camera driver '%s' (%s)."), camera->pc->a.library,
 			lt_dlerror ());
 		lt_dlexit ();
+		gpi_libltdl_unlock();
 		return (GP_ERROR_LIBRARY);
 	}
 
 	/* Initialize the camera */
+	gpi_libltdl_lock();
 	init_func = lt_dlsym (camera->pc->lh, "camera_init");
+	gpi_libltdl_unlock();
 	if (!init_func) {
+		gpi_libltdl_lock();
 		lt_dlclose (camera->pc->lh);
 		lt_dlexit ();
+		gpi_libltdl_unlock();
 		camera->pc->lh = NULL;
 		gp_context_error (context, _("Camera driver '%s' is "
 			"missing the 'camera_init' function."),
@@ -802,8 +813,10 @@ gp_camera_init (Camera *camera, GPContext *context)
 	if (strcasecmp (camera->pc->a.model, "Directory Browse")) {
 		result = gp_port_open (camera->port);
 		if (result < 0) {
+			gpi_libltdl_lock();
 			lt_dlclose (camera->pc->lh);
 			lt_dlexit ();
+			gpi_libltdl_unlock();
 			camera->pc->lh = NULL;
 			return (result);
 		}
@@ -812,8 +825,10 @@ gp_camera_init (Camera *camera, GPContext *context)
 	result = init_func (camera, context);
 	if (result < 0) {
 		gp_port_close (camera->port);
+		gpi_libltdl_lock();
 		lt_dlclose (camera->pc->lh);
 		lt_dlexit ();
+		gpi_libltdl_unlock();
 		camera->pc->lh = NULL;
 		memset (camera->functions, 0, sizeof (CameraFunctions));
 		return (result);