Work around API misuse in gutenprint
https://bugzilla.redhat.com/show_bug.cgi?id=2056326
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Benjamin Berg
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2 changed files with 179 additions and 0 deletions
175
0001-core-Install-first-context-as-implicit-default.patch
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175
0001-core-Install-first-context-as-implicit-default.patch
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From f74f1e21b6201ec803347ddaf2737cdaf9a1180a Mon Sep 17 00:00:00 2001
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From: Benjamin Berg <bberg@redhat.com>
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Date: Tue, 22 Feb 2022 11:45:38 +0100
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Subject: [PATCH] core: Install first context as implicit default
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There was a behaviour change in libusb, which triggers issues when the
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API is misused. This caused gutenprint to crash, see
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https://bugzilla.redhat.com/show_bug.cgi?id=2055504
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For now, work around this by installing an implicit default. But, change
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the code to log an error in case this "feature" is being used.
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---
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libusb/core.c | 24 ++++++++++++++++--------
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libusb/libusbi.h | 8 +++++++-
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tests/umockdev.c | 26 ++++++++++++++++++++++++++
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3 files changed, 49 insertions(+), 9 deletions(-)
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diff --git a/libusb/core.c b/libusb/core.c
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index 1c1ada1..c56df72 100644
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--- a/libusb/core.c
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+++ b/libusb/core.c
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@@ -41,7 +41,7 @@ static libusb_log_cb log_handler;
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#endif
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struct libusb_context *usbi_default_context;
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-static int default_context_refcnt;
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+int usbi_default_context_refcnt;
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static usbi_mutex_static_t default_context_lock = USBI_MUTEX_INITIALIZER;
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static struct usbi_option default_context_options[LIBUSB_OPTION_MAX];
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@@ -2284,9 +2284,9 @@ int API_EXPORTED libusb_init(libusb_context **ctx)
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usbi_mutex_static_lock(&default_context_lock);
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- if (!ctx && usbi_default_context) {
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+ if (!ctx && usbi_default_context_refcnt > 0) {
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usbi_dbg(usbi_default_context, "reusing default context");
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- default_context_refcnt++;
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+ usbi_default_context_refcnt++;
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usbi_mutex_static_unlock(&default_context_lock);
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return 0;
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}
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@@ -2331,7 +2331,7 @@ int API_EXPORTED libusb_init(libusb_context **ctx)
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/* default context must be initialized before calling usbi_dbg */
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if (!ctx) {
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usbi_default_context = _ctx;
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- default_context_refcnt = 1;
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+ usbi_default_context_refcnt = 1;
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usbi_dbg(usbi_default_context, "created default context");
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}
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@@ -2357,6 +2357,12 @@ int API_EXPORTED libusb_init(libusb_context **ctx)
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if (ctx)
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*ctx = _ctx;
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+ if (usbi_default_context == NULL) {
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+ usbi_default_context = _ctx;
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+ usbi_default_context_refcnt = 0;
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+ usbi_dbg(usbi_default_context, "installing new context as implicit default");
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+ }
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+
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usbi_mutex_static_unlock(&default_context_lock);
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return 0;
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@@ -2373,7 +2379,7 @@ err_free_ctx:
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if (!ctx) {
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/* clear default context that was not fully initialized */
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usbi_default_context = NULL;
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- default_context_refcnt = 0;
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+ usbi_default_context_refcnt = 0;
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}
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usbi_mutex_destroy(&_ctx->open_devs_lock);
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@@ -2407,7 +2413,7 @@ void API_EXPORTED libusb_exit(libusb_context *ctx)
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return;
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}
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- if (--default_context_refcnt > 0) {
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+ if (--usbi_default_context_refcnt > 0) {
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usbi_dbg(ctx, "not destroying default context");
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usbi_mutex_static_unlock(&default_context_lock);
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return;
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@@ -2427,8 +2433,10 @@ void API_EXPORTED libusb_exit(libusb_context *ctx)
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if (usbi_backend.exit)
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usbi_backend.exit(_ctx);
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- if (!ctx)
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+ if (!ctx || ctx == usbi_default_context) {
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usbi_default_context = NULL;
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+ assert(usbi_default_context_refcnt == 0);
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+ }
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usbi_mutex_static_unlock(&default_context_lock);
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@@ -2575,7 +2583,7 @@ static void log_v(struct libusb_context *ctx, enum libusb_log_level level,
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#else
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enum libusb_log_level ctx_level;
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- ctx = usbi_get_context(ctx);
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+ ctx = ctx ? ctx : usbi_default_context;
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if (ctx)
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ctx_level = ctx->debug;
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else
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diff --git a/libusb/libusbi.h b/libusb/libusbi.h
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index 5f0d5c2..a404cff 100644
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--- a/libusb/libusbi.h
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+++ b/libusb/libusbi.h
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@@ -436,13 +436,19 @@ struct libusb_context {
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};
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extern struct libusb_context *usbi_default_context;
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+extern int usbi_default_context_refcnt;
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extern struct list_head active_contexts_list;
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extern usbi_mutex_static_t active_contexts_lock;
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static inline struct libusb_context *usbi_get_context(struct libusb_context *ctx)
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{
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- return ctx ? ctx : usbi_default_context;
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+ if (!ctx && usbi_default_context) {
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+ if (usbi_default_context_refcnt == 0)
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+ usbi_err(usbi_default_context, "API misuse! Using non-default context as implicit default.");
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+ ctx = usbi_default_context;
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+ }
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+ return ctx;
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}
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enum usbi_event_flags {
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diff --git a/tests/umockdev.c b/tests/umockdev.c
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index b2af512..7de0aae 100644
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--- a/tests/umockdev.c
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+++ b/tests/umockdev.c
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@@ -551,6 +551,27 @@ test_open_close(UMockdevTestbedFixture * fixture, UNUSED_DATA)
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libusb_close(handle);
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}
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+static void
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+test_implicit_default(UMockdevTestbedFixture * fixture, UNUSED_DATA)
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+{
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+ libusb_device **devs = NULL;
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+
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+ clear_libusb_log(fixture, LIBUSB_LOG_LEVEL_INFO);
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+ g_assert_cmpint(libusb_get_device_list(NULL, &devs), ==, 1);
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+ libusb_free_device_list(devs, TRUE);
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+ assert_libusb_log_msg(fixture, LIBUSB_LOG_LEVEL_ERROR, "\\[usbi_get_context\\].*implicit default");
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+
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+ libusb_init(NULL);
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+ g_assert_cmpint(libusb_get_device_list(NULL, &devs), ==, 1);
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+ libusb_exit(NULL);
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+
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+ /* We free late, causing a warning from libusb_exit. However,
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+ * we never see this warning (i.e. test success) because it is on a
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+ * different context.
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+ */
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+ libusb_free_device_list(devs, TRUE);
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+}
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+
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static void
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test_close_flying(UMockdevTestbedFixture * fixture, UNUSED_DATA)
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{
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@@ -932,6 +953,11 @@ main(int argc, char **argv)
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test_open_close,
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test_fixture_teardown);
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+ g_test_add("/libusb/implicit-default", UMockdevTestbedFixture, NULL,
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+ test_fixture_setup_with_canon,
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+ test_implicit_default,
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+ test_fixture_teardown);
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+
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g_test_add("/libusb/close-flying", UMockdevTestbedFixture, NULL,
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test_fixture_setup_with_canon,
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test_close_flying,
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--
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2.35.1
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@ -21,6 +21,10 @@ Patch0002: https://github.com/libusb/libusb/pull/1073.patch
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# Add umockdev based tests from https://github.com/libusb/libusb/pull/1078
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Patch0003: 0001-tests-Add-some-umockdev-based-tests.patch
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# Work around API misuse in gutenprint
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# https://bugzilla.redhat.com/show_bug.cgi?id=2056326
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Patch9999: 0001-core-Install-first-context-as-implicit-default.patch
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%description
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This package provides a way for applications to access USB devices.
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