@@ -235,6 +235,10 @@ if [ "$ASAN" ]; then
CFLAGS_FOR_OVS="${CFLAGS_FOR_OVS} -O1"
fi
+if [ "$RCU_BLOCK" ]; then
+ EXTRA_OPTS="$EXTRA_OPTS --enable-rcu-blocking"
+fi
+
save_OPTS="${OPTS} $*"
OPTS="${EXTRA_OPTS} ${save_OPTS}"
@@ -23,6 +23,7 @@ jobs:
M32: ${{ matrix.m32 }}
OPTS: ${{ matrix.opts }}
TESTSUITE: ${{ matrix.testsuite }}
+ RCU_BLOCK: ${{ matrix.rcu_blocking }}
name: linux ${{ join(matrix.*, ' ') }}
runs-on: ubuntu-18.04
@@ -109,6 +110,12 @@ jobs:
- compiler: gcc
deb_package: deb
+ - compiler: clang
+ testsuite: test
+ kernel: 3.16
+ asan: asan
+ rcu_blocking: rcu-blocking
+
steps:
- name: checkout
uses: actions/checkout@v2
@@ -10,6 +10,7 @@ Post-v2.15.0
in ovsdb on startup.
* New command 'record-hostname-if-not-set' to update hostname in ovsdb.
- New --enable-asan configure option enables AddressSanitizer.
+ - New --enable-rcu-blocking configure option to debug RCU usage.
v2.15.0 - 15 Feb 2021
@@ -1386,6 +1386,21 @@ AC_DEFUN([OVS_ENABLE_SPARSE],
[], [enable_sparse=no])
AM_CONDITIONAL([ENABLE_SPARSE_BY_DEFAULT], [test $enable_sparse = yes])])
+dnl OVS_ENABLE_RCU_BLOCKING
+AC_DEFUN([OVS_ENABLE_RCU_BLOCKING],
+ [AC_ARG_ENABLE(
+ [rcu-blocking],
+ [AC_HELP_STRING([--enable-rcu-blocking],
+ [Enable the blocking RCU mode])],
+ [RCU_BLOCKING=yes], [RCU_BLOCKING=no])
+ AC_SUBST([RCU_BLOCKING])
+ AC_CONFIG_COMMANDS_PRE([
+ if test "$RCU_BLOCKING" = "yes"; then
+ OVS_CFLAGS="$OVS_CFLAGS -DOVS_RCU_BLOCKING=1"
+ fi
+ ])
+ ])
+
dnl OVS_CTAGS_IDENTIFIERS
dnl
dnl ctags ignores symbols with extras identifiers. This is a list of
@@ -184,6 +184,7 @@ OVS_CHECK_CC_OPTION([-mavx512f], [CFLAGS="$CFLAGS -DHAVE_AVX512F"])
OVS_ENABLE_WERROR
OVS_ENABLE_ASAN
OVS_ENABLE_SPARSE
+OVS_ENABLE_RCU_BLOCKING
OVS_CTAGS_IDENTIFIERS
OVS_CHECK_DPCLS_AUTOVALIDATOR
OVS_CHECK_BINUTILS_AVX512
@@ -71,6 +71,81 @@ static void ovsrcu_unregister__(struct ovsrcu_perthread *);
static bool ovsrcu_call_postponed(void);
static void *ovsrcu_postpone_thread(void *arg OVS_UNUSED);
+#ifdef OVS_RCU_BLOCKING
+
+static struct seq *postpone_wait;
+DEFINE_STATIC_PER_THREAD_DATA(bool, need_wait, false);
+DEFINE_STATIC_PER_THREAD_DATA(uint64_t, quiescent_seqno, 0);
+
+static bool
+ovsrcu_exited(void)
+{
+ /* Do not wait on the postpone thread if it has been cleared for exit. */
+ return single_threaded() || latch_is_set(&postpone_exit);
+}
+
+static void
+ovsrcu_postpone_end(void)
+{
+ seq_change(postpone_wait);
+}
+
+static void
+ovsrcu_postpone_wait_enable(bool seq_locked)
+{
+ if (strncmp(get_subprogram_name(), "urcu", strlen("urcu")) &&
+ !ovsrcu_exited()) {
+
+ if (seq_locked) {
+ *quiescent_seqno_get() = seq_read_protected(postpone_wait);
+ } else {
+ *quiescent_seqno_get() = seq_read(postpone_wait);
+ }
+
+ *need_wait_get() = true;
+ }
+}
+
+static void
+ovsrcu_postpone_wait(void)
+{
+ struct ovsrcu_perthread *perthread;
+ uint64_t last_seqno_seen;
+
+ ovsrcu_init_module();
+
+ if (strncmp(get_subprogram_name(), "urcu", strlen("urcu")) &&
+ !ovsrcu_exited() && *need_wait_get()) {
+ *need_wait_get() = false;
+
+ last_seqno_seen = *quiescent_seqno_get();
+ if (last_seqno_seen != seq_read(postpone_wait)) {
+ return;
+ }
+
+ seq_wait(postpone_wait, *quiescent_seqno_get());
+
+ /* Unregistering the potential current perthread
+ * marks this thread as quiescent.
+ */
+ perthread = pthread_getspecific(perthread_key);
+ if (perthread) {
+ pthread_setspecific(perthread_key, NULL);
+ ovsrcu_unregister__(perthread);
+ }
+
+ poll_block();
+ }
+}
+
+#else
+
+#define ovsrcu_postpone_end() do { } while (0)
+#define ovsrcu_postpone_wait_enable(b) do { } while (0)
+#define ovsrcu_postpone_wait() do { } while (0)
+
+#endif /* OVS_RCU_BLOCKING */
+
static struct ovsrcu_perthread *
ovsrcu_perthread_get(void)
{
@@ -122,6 +197,7 @@ ovsrcu_quiesced(void)
ovsthread_once_done(&once);
}
}
+ ovsrcu_postpone_wait();
}
/* Indicates the beginning of a quiescent state. See "Details" near the top of
@@ -154,6 +230,7 @@ ovsrcu_quiesce(void)
perthread = ovsrcu_perthread_get();
perthread->seqno = seq_read(global_seqno);
if (perthread->cbset) {
+ ovsrcu_postpone_wait_enable(false);
ovsrcu_flush_cbset(perthread);
}
seq_change(global_seqno);
@@ -172,6 +249,7 @@ ovsrcu_try_quiesce(void)
if (!seq_try_lock()) {
perthread->seqno = seq_read_protected(global_seqno);
if (perthread->cbset) {
+ ovsrcu_postpone_wait_enable(true);
ovsrcu_flush_cbset__(perthread, true);
}
seq_change_protected(global_seqno);
@@ -359,7 +437,9 @@ ovsrcu_postpone_thread(void *arg OVS_UNUSED)
while (!latch_is_set(&postpone_exit)) {
uint64_t seqno = seq_read(flushed_cbsets_seq);
- if (!ovsrcu_call_postponed()) {
+ bool postpone_executed = ovsrcu_call_postponed();
+ ovsrcu_postpone_end();
+ if (!postpone_executed) {
seq_wait(flushed_cbsets_seq, seqno);
latch_wait(&postpone_exit);
poll_block();
@@ -397,6 +477,7 @@ static void
ovsrcu_unregister__(struct ovsrcu_perthread *perthread)
{
if (perthread->cbset) {
+ ovsrcu_postpone_wait_enable(false);
ovsrcu_flush_cbset(perthread);
}
@@ -432,6 +513,9 @@ ovsrcu_init_module(void)
{
static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
if (ovsthread_once_start(&once)) {
+#ifdef OVS_RCU_BLOCKING
+ postpone_wait = seq_create();
+#endif
global_seqno = seq_create();
xpthread_key_create(&perthread_key, ovsrcu_thread_exit_cb);
fatal_signal_add_hook(ovsrcu_cancel_thread_exit_cb, NULL, NULL, true);
@@ -4,6 +4,7 @@ OPENSSL_SUPPORTS_SNI='@OPENSSL_SUPPORTS_SNI@'
HAVE_UNBOUND='@HAVE_UNBOUND@'
EGREP='@EGREP@'
PYTHON3='@PYTHON3@'
+RCU_BLOCKING='@RCU_BLOCKING@'
# PYTHONCOERCECLOCALE=0 disables the Unicode compatibility warning on
# stderr that breaks almost any Python3 test (PEP 0538)
@@ -264,6 +264,7 @@ AT_CLEANUP
AT_SETUP([rcu quiesce use-after-free detection])
AT_SKIP_IF([test "$IS_WIN32" = "yes"])
AT_SKIP_IF([test "$ASAN_ENABLED" = "no"])
+AT_SKIP_IF([test "$RCU_BLOCKING" = "no"])
# SIGABRT + 128
exit_status=134
AT_KEYWORDS([rcu asan])
@@ -275,6 +276,7 @@ AT_CLEANUP
AT_SETUP([rcu try-quiesce use-after-free detection])
AT_SKIP_IF([test "$IS_WIN32" = "yes"])
AT_SKIP_IF([test "$ASAN_ENABLED" = "no"])
+AT_SKIP_IF([test "$RCU_BLOCKING" = "no"])
# SIGABRT + 128
exit_status=134
AT_KEYWORDS([rcu asan])
@@ -286,6 +288,7 @@ AT_CLEANUP
AT_SETUP([rcu quiesce-start-end use-after-free detection])
AT_SKIP_IF([test "$IS_WIN32" = "yes"])
AT_SKIP_IF([test "$ASAN_ENABLED" = "no"])
+AT_SKIP_IF([test "$RCU_BLOCKING" = "no"])
AT_KEYWORDS([rcu asan])
# SIGABRT + 128
exit_status=134
Add the configure option --enable-rcu-blocking, that modifies the RCU library. When enabled, quiescing from other threads will block, waiting on the RCU thread to execute the postponed jobs. This mode forces the deferred memory reclamation to happen deterministically, reducing the latency of the deferral and forcing memory to be freed any time a thread goes through a quiescent state. Some use-after-free that were hidden by deferred memory reclamation may become observable as a result. Previously the RCU mechanism would make them harder to detect. UAF detection tools should then be used in conjunction with this compilation flag, e.g. (assuming llvm installed): ./configure --enable-rcu-blocking --enable-asan export ASAN_SYMBOLIZER_PATH=$(which llvm-symbolizer) export ASAN_OPTIONS=symbolize=1 make # Verify the tool works: should trigger a UAF ./tests/ovstest test-rcu-uaf quiesce ./tests/ovstest test-rcu-uaf try-quiesce ./tests/ovstest test-rcu-uaf quiesce-start-end # The testsuite can be used as well make check TESTSUITEFLAGS='-k rcu' Signed-off-by: Gaetan Rivet <grive@u256.net> --- .ci/linux-build.sh | 4 ++ .github/workflows/build-and-test.yml | 7 +++ NEWS | 1 + acinclude.m4 | 15 +++++ configure.ac | 1 + lib/ovs-rcu.c | 86 +++++++++++++++++++++++++++- tests/atlocal.in | 1 + tests/library.at | 3 + 8 files changed, 117 insertions(+), 1 deletion(-)