core: Do not attempt to destroy a default context that doesn't exist

Calling libusb_exit(NULL) when a successful call to libusb_init(NULL)
has not been made results in a segmentation violation. This is
definitely a user error, but we can easily guard against it.

Closes #511

Signed-off-by: Chris Dickens <christopher.a.dickens@gmail.com>

diff --git a/libusb/core.c b/libusb/core.c
index 5c0a2e0..26df871 100644 (file)
--- a/libusb/core.c
+++ b/libusb/core.c
@@ -2305,7 +2305,7 @@ int API_EXPORTED libusb_init(libusb_context **context)
        usbi_mutex_static_lock(&active_contexts_lock);
        if (first_init) {
                first_init = 0;
-               list_init (&active_contexts_list);
+               list_init(&active_contexts_list);
        }
        list_add (&ctx->list, &active_contexts_list);
        usbi_mutex_static_unlock(&active_contexts_lock);
@@ -2337,7 +2337,7 @@ err_free_ctx:
        }
 
        usbi_mutex_static_lock(&active_contexts_lock);
-       list_del (&ctx->list);
+       list_del(&ctx->list);
        usbi_mutex_static_unlock(&active_contexts_lock);
 
        usbi_mutex_lock(&ctx->usb_devs_lock);
@@ -2375,6 +2375,12 @@ void API_EXPORTED libusb_exit(struct libusb_context *ctx)
         * if we're the last user */
        usbi_mutex_static_lock(&default_context_lock);
        if (ctx == usbi_default_context) {
+               if (!usbi_default_context) {
+                       usbi_dbg("no default context, not initialized?");
+                       usbi_mutex_static_unlock(&default_context_lock);
+                       return;
+               }
+
                if (--default_context_refcnt > 0) {
                        usbi_dbg("not destroying default context");
                        usbi_mutex_static_unlock(&default_context_lock);
@@ -2390,12 +2396,12 @@ void API_EXPORTED libusb_exit(struct libusb_context *ctx)
                 */
                destroying_default_context = 1;
        } else {
-               // Unlock default context, as we're not modifying it.
+               /* Unlock default context, as we're not modifying it. */
                usbi_mutex_static_unlock(&default_context_lock);
-  }
+       }
 
        usbi_mutex_static_lock(&active_contexts_lock);
-       list_del (&ctx->list);
+       list_del(&ctx->list);
        usbi_mutex_static_unlock(&active_contexts_lock);
 
        if (libusb_has_capability(LIBUSB_CAP_HAS_HOTPLUG)) {

diff --git a/libusb/version_nano.h b/libusb/version_nano.h
index 57c2b1d..3247cec 100644 (file)
--- a/libusb/version_nano.h
+++ b/libusb/version_nano.h
@@ -1 +1 @@
-#define LIBUSB_NANO 11426
+#define LIBUSB_NANO 11427