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Only access non-locals after they're initialised #40

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30 changes: 24 additions & 6 deletions src/preload.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -37,8 +37,23 @@

static std::mutex g_rules_mutex;

static std::once_flag g_rules_init_flag;
static std::shared_ptr<const std::vector<Rule>> g_rules = nullptr;

/*
* This is needed because non-local initialisation is not guaranteed to have
* happened as soon as one of our wrapper functions is called.
*/
static bool g_initialised = false;

__attribute__((constructor(65535))) void mark_initialised(void) {
g_initialised = true;
}

__attribute__((destructor(65535))) void mark_uninitialised(void) {
g_initialised = false;
}

using RuleMatch = std::optional<std::pair<size_t, const Rule>>;

static void init_rules(void)
Expand Down Expand Up @@ -170,7 +185,7 @@ extern "C" int WRAP_SYM(listen)(int sockfd, int backlog)
static RuleMatch match_rule(const SockAddr &addr, const Socket::Ptr sock,
const RuleDir dir)
{
init_rules();
std::call_once(g_rules_init_flag, init_rules);

size_t rulepos = 0;
for (
Expand Down Expand Up @@ -318,11 +333,11 @@ static inline int bind_connect(SockFun &&sockfun, RealFun &&realfun,
RuleDir dir, int fd,
const struct sockaddr *addr, socklen_t addrlen)
{
if (
if (!g_initialised || (
addr->sa_family != AF_INET &&
addr->sa_family != AF_INET6 &&
addr->sa_family != AF_UNIX
) return std::invoke(realfun, fd, addr, addrlen);
)) return std::invoke(realfun, fd, addr, addrlen);

// NOLINTNEXTLINE(performance-unnecessary-value-param)
return Socket::when<int>(fd, [&](Socket::Ptr sock) {
Expand Down Expand Up @@ -535,7 +550,7 @@ extern "C" ssize_t WRAP_SYM(sendto)(int fd, const void *buf, size_t len,
{
TRACE_CALL("sendto", fd, buf, len, flags, addr, addrlen);

if (addr == nullptr)
if (!g_initialised || addr == nullptr)
return real::sendto(fd, buf, len, flags, addr, addrlen);

// NOLINTNEXTLINE(performance-unnecessary-value-param)
Expand Down Expand Up @@ -583,7 +598,7 @@ extern "C" ssize_t WRAP_SYM(sendmsg)(int fd, const struct msghdr *msg,
{
TRACE_CALL("sendmsg", fd, msg, flags);

if (msg->msg_name == nullptr)
if (!g_initialised || msg->msg_name == nullptr)
return real::sendmsg(fd, msg, flags);

// NOLINTNEXTLINE(performance-unnecessary-value-param)
Expand Down Expand Up @@ -671,10 +686,13 @@ extern "C" int WRAP_SYM(close)(int fd)
{
TRACE_CALL("close", fd);

if (!g_initialised)
return real::close(fd);

#ifdef SYSTEMD_SUPPORT
{
std::scoped_lock<std::mutex> lock(g_rules_mutex);
init_rules();
std::call_once(g_rules_init_flag, init_rules);
if (Systemd::has_fd(fd)) {
LOG(DEBUG) << "Prevented socket fd " << fd << " from being closed,"
<< " because it's a file descriptor passed by systemd.";
Expand Down
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