From d7f8d239cb49775a1fe7765d6edb463d7fe669e1 Mon Sep 17 00:00:00 2001 From: Chris Dickens Date: Mon, 13 Jan 2020 15:05:00 -0800 Subject: [PATCH 7/8] 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 --- libusb/core.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/libusb/core.c b/libusb/core.c index 82a5d03..3b6a265 100644 --- a/libusb/core.c +++ b/libusb/core.c @@ -2304,7 +2304,7 @@ 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); @@ -2336,7 +2336,7 @@ 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); @@ -2374,6 +2374,12 @@ 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); @@ -2389,12 +2395,12 @@ 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)) { -- 2.27.0.windows.1