10:47 a.m.
Build using Address Sanitizer (asan), Leak Sanitizer (lsan), or
Undefined Behavior Sanitizer (ubsan) by using one of these options for
the configure script:
--enable-asan
--enable-lsan
--enable-ubsan
For each of these to work, the compiler must support the requested
sanitizer and the requisite libraries must be installed (libasan,
liblsan, libubsan).
---
acinclude.m4 | 36 ++++++++++++++++++++++++++++++++++++
configure.ac | 45 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 81 insertions(+)
diff --git a/acinclude.m4 b/acinclude.m4
index 0ba4287..8aab4ee 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -10,6 +10,42 @@ AC_DEFUN([AC_PROG_CC_PIE], [
])
])
+AC_DEFUN([AC_PROG_CC_ASAN], [
+ AC_CACHE_CHECK([whether ${CC-cc} accepts -fsanitize=address], ac_cv_prog_cc_asan, [
+ echo 'void f(){}' > conftest.c
+ if test -z "`${CC-cc} -fsanitize=address -c conftest.c 2>&1`"; then
+ ac_cv_prog_cc_asan=yes
+ else
+ ac_cv_prog_cc_asan=no
+ fi
+ rm -rf conftest*
+ ])
+])
+
+AC_DEFUN([AC_PROG_CC_LSAN], [
+ AC_CACHE_CHECK([whether ${CC-cc} accepts -fsanitize=leak], ac_cv_prog_cc_lsan, [
+ echo 'void f(){}' > conftest.c
+ if test -z "`${CC-cc} -fsanitize=leak -c conftest.c 2>&1`"; then
+ ac_cv_prog_cc_lsan=yes
+ else
+ ac_cv_prog_cc_lsan=no
+ fi
+ rm -rf conftest*
+ ])
+])
+
+AC_DEFUN([AC_PROG_CC_UBSAN], [
+ AC_CACHE_CHECK([whether ${CC-cc} accepts -fsanitize=undefined], ac_cv_prog_cc_ubsan, [
+ echo 'void f(){}' > conftest.c
+ if test -z "`${CC-cc} -fsanitize=undefined -c conftest.c 2>&1`"; then
+ ac_cv_prog_cc_ubsan=yes
+ else
+ ac_cv_prog_cc_ubsan=no
+ fi
+ rm -rf conftest*
+ ])
+])
+
AC_DEFUN([COMPILER_FLAGS], [
if (test "${CFLAGS}" = ""); then
CFLAGS="-Wall -O2 -fsigned-char"
diff --git a/configure.ac b/configure.ac
index 39755fe..e4ca5b2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -20,6 +20,9 @@ AC_LANG_C
AC_PROG_CC
AC_PROG_CC_PIE
+AC_PROG_CC_ASAN
+AC_PROG_CC_LSAN
+AC_PROG_CC_UBSAN
AC_PROG_INSTALL
AC_C_CHAR_UNSIGNED
@@ -54,6 +57,48 @@ AC_ARG_ENABLE(pie, AC_HELP_STRING([--enable-pie],
fi
])
+save_LIBS=$LIBS
+AC_CHECK_LIB(asan, __sanitizer_cov_init)
+LIBS=$save_LIBS
+
+AC_ARG_ENABLE(asan, AC_HELP_STRING([--enable-asan],
+ [enable linking with address sanitizer]), [
+ if (test "${enableval}" = "yes" &&
+ test "${ac_cv_lib_asan___sanitizer_cov_init}" = "yes" &&
+ test "${ac_cv_prog_cc_asan}" = "yes"); then
+ CFLAGS="$CFLAGS -fsanitize=address";
+ LDFLAGS="$LDFLAGS -fsanitize=address"
+ fi
+])
+
+save_LIBS=$LIBS
+AC_CHECK_LIB(lsan, __sanitizer_cov_init)
+LIBS=$save_LIBS
+
+AC_ARG_ENABLE(lsan, AC_HELP_STRING([--enable-lsan],
+ [enable linking with leak sanitizer]), [
+ if (test "${enableval}" = "yes" &&
+ test "${ac_cv_lib_lsan___sanitizer_cov_init}" = "yes" &&
+ test "${ac_cv_prog_cc_lsan}" = "yes"); then
+ CFLAGS="$CFLAGS -fsanitize=leak";
+ LDFLAGS="$LDFLAGS -fsanitize=leak"
+ fi
+])
+
+save_LIBS=$LIBS
+AC_CHECK_LIB(ubsan, __sanitizer_cov_init)
+LIBS=$save_LIBS
+
+AC_ARG_ENABLE(ubsan, AC_HELP_STRING([--enable-ubsan],
+ [enable linking with undefined behavior sanitizer]), [
+ if (test "${enableval}" = "yes" &&
+ test "${ac_cv_lib_ubsan___sanitizer_cov_init}" = "yes"
&&
+ test "${ac_cv_prog_cc_ubsan}" = "yes"); then
+ CFLAGS="$CFLAGS -fsanitize=undefined";
+ LDFLAGS="$LDFLAGS -fsanitize=undefined"
+ fi
+])
+
AC_CHECK_FUNC(signalfd, dummy=yes,
AC_MSG_ERROR(signalfd support is required))
--
2.7.3
10:47 a.m.
New subject: [PATCH 2/3] unit: Add race condition test to test-main
This test excercises the case where multiple events are returned from
the same epoll_wait call and an early event deletes a watch that is
waiting to be processed in the same event loop iteration.
---
unit/test-main.c | 35 +++++++++++++++++++++++++++++++----
1 file changed, 31 insertions(+), 4 deletions(-)
diff --git a/unit/test-main.c b/unit/test-main.c
index b61e337..3ee78f5 100644
--- a/unit/test-main.c
+++ b/unit/test-main.c
@@ -25,6 +25,7 @@
#endif
#include <ell/ell.h>
+#include <unistd.h>
static void signal_handler(struct l_signal *signal, uint32_t signo,
void *user_data)
@@ -38,7 +39,7 @@ static void signal_handler(struct l_signal *signal, uint32_t signo,
}
}
-static void timeout_handler(struct l_timeout *timeout, void *user_data)
+static void timeout_quit_handler(struct l_timeout *timeout, void *user_data)
{
l_main_quit();
}
@@ -58,9 +59,25 @@ static void oneshot_handler(void *user_data)
l_info("One-shot");
}
+static void race_delay_handler(struct l_timeout *timeout, void *user_data)
+{
+ usleep(250 * 1000);
+}
+
+static void race_handler(struct l_timeout *timeout, void *user_data)
+{
+ struct l_timeout **other_racer = user_data;
+
+ l_timeout_remove(*other_racer);
+ *other_racer = NULL;
+}
+
int main(int argc, char *argv[])
{
- struct l_timeout *timeout;
+ struct l_timeout *timeout_quit;
+ struct l_timeout *race_delay;
+ struct l_timeout *race1;
+ struct l_timeout *race2;
struct l_signal *signal;
struct l_idle *idle;
sigset_t mask;
@@ -71,7 +88,13 @@ int main(int argc, char *argv[])
signal = l_signal_create(&mask, signal_handler, NULL, NULL);
- timeout = l_timeout_create(3, timeout_handler, NULL, NULL);
+ timeout_quit = l_timeout_create(3, timeout_quit_handler, NULL, NULL);
+
+ race_delay = l_timeout_create(1, race_delay_handler, NULL, NULL);
+ race1 = l_timeout_create_with_nanoseconds(1, 100000000, race_handler,
+ &race2, NULL);
+ race2 = l_timeout_create_with_nanoseconds(1, 100000000, race_handler,
+ &race1, NULL);
idle = l_idle_create(idle_handler, NULL, NULL);
@@ -85,7 +108,11 @@ int main(int argc, char *argv[])
l_main_run();
- l_timeout_remove(timeout);
+ l_timeout_remove(race_delay);
+ l_timeout_remove(race1);
+ l_timeout_remove(race2);
+
+ l_timeout_remove(timeout_quit);
l_signal_remove(signal);
--
2.7.3
10:47 a.m.
New subject: [PATCH 3/3] main: Safely free watch_data structures
The race condition test in test-main exposed a case where the events
array returned by epoll_wait could have a stale watch_data
pointer. This triggered a use-after-free error that was reported by
the address sanitizer (./configure --enable-asan).
When the event loop is running, watch_remove now queues the watch_data
structure to be freed later. The watch_data callback is modified so
that a safe function is executed if the event loop attempts a callback
on a pending removed watch. Any queued watch_data structures are freed
at the end of each event loop iteration.
---
ell/main.c | 28 +++++++++++++++++++++++++++-
1 file changed, 27 insertions(+), 1 deletion(-)
diff --git a/ell/main.c b/ell/main.c
index f8fa4ac..135a6da 100644
--- a/ell/main.c
+++ b/ell/main.c
@@ -56,6 +56,7 @@ static int idle_id;
static int exit_status = EXIT_FAILURE;
static struct l_queue *idle_list;
+static struct l_queue *watch_free_list;
struct watch_data {
int fd;
@@ -101,6 +102,10 @@ static inline bool __attribute__ ((always_inline))
create_epoll(void)
idle_id = 0;
+ watch_free_list = l_queue_new();
+ if (!watch_free_list)
+ goto free_idle_list;
+
watch_entries = DEFAULT_WATCH_ENTRIES;
for (i = 0; i < watch_entries; i++)
@@ -108,6 +113,10 @@ static inline bool __attribute__ ((always_inline))
create_epoll(void)
return true;
+free_idle_list:
+ l_queue_destroy(idle_list, NULL);
+ idle_list = NULL;
+
free_watch_list:
free(watch_list);
watch_list = NULL;
@@ -190,6 +199,11 @@ int watch_modify(int fd, uint32_t events, bool force)
return 0;
}
+static void watch_nop_callback(int fd, uint32_t events, void *user_data)
+{
+ return;
+}
+
int watch_remove(int fd)
{
struct watch_data *data;
@@ -212,7 +226,15 @@ int watch_remove(int fd)
if (data->destroy)
data->destroy(data->user_data);
- l_free(data);
+ if (epoll_running) {
+ /* The epoll events array may point to the same memory as
+ * 'data', so let the event loop free it later
+ */
+ data->callback = watch_nop_callback;
+ l_queue_push_tail(watch_free_list, data);
+ } else {
+ l_free(data);
+ }
return err;
}
@@ -352,6 +374,7 @@ LIB_EXPORT int l_main_run(void)
l_queue_foreach(idle_list, idle_dispatch, NULL);
l_queue_foreach_remove(idle_list, idle_prune, NULL);
+ l_queue_clear(watch_free_list, l_free);
}
for (i = 0; i < watch_entries; i++) {
@@ -378,6 +401,9 @@ LIB_EXPORT int l_main_run(void)
l_queue_destroy(idle_list, idle_destroy);
idle_list = NULL;
+ l_queue_destroy(watch_free_list, l_free);
+ watch_free_list = NULL;
+
epoll_running = false;
close(epoll_fd);
--
2.7.3
2337
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2337
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Mat Martineau