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src: restore stdio on program exit
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Record the state of the stdio file descriptors on start-up and restore
them to that state on exit.  This should prevent issues where node.js
sometimes leaves stdio in raw or non-blocking mode.

Co-authored-by: Krzysztof Taborski <taborskikrzysztof@gmail.com>
PR-URL: #20592
Fixes: #14752
Fixes: #21020
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
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2 people authored and addaleax committed May 31, 2018
1 parent 182c73b commit af06581
Showing 1 changed file with 94 additions and 6 deletions.
100 changes: 94 additions & 6 deletions src/node.cc
Original file line number Diff line number Diff line change
Expand Up @@ -100,6 +100,7 @@ typedef int mode_t;
#else
#include <pthread.h>
#include <sys/resource.h> // getrlimit, setrlimit
#include <termios.h> // tcgetattr, tcsetattr
#include <unistd.h> // setuid, getuid
#endif

Expand Down Expand Up @@ -172,6 +173,9 @@ using v8::Value;
static Mutex process_mutex;
static Mutex environ_mutex;

// Safe to call more than once and from signal handlers.
inline void PlatformExit();

static bool print_eval = false;
static bool force_repl = false;
static bool syntax_check_only = false;
Expand Down Expand Up @@ -1091,7 +1095,7 @@ void AppendExceptionLine(Environment* env,
Mutex::ScopedLock lock(process_mutex);
env->set_printed_error(true);

uv_tty_reset_mode();
PlatformExit();
PrintErrorString("\n%s", arrow);
return;
}
Expand Down Expand Up @@ -3025,7 +3029,7 @@ void SetupProcessObject(Environment* env,


void SignalExit(int signo) {
uv_tty_reset_mode();
PlatformExit();
v8_platform.StopTracingAgent();
#ifdef __FreeBSD__
// FreeBSD has a nasty bug, see RegisterSignalHandler for details
Expand Down Expand Up @@ -3846,6 +3850,27 @@ static void DebugEnd(const FunctionCallbackInfo<Value>& args) {
}


#ifdef __POSIX__
static struct {
int flags;
bool isatty;
struct stat stat;
struct termios termios;
} stdio[1 + STDERR_FILENO];


inline int GetFileDescriptorFlags(int fd) {
int flags;

do {
flags = fcntl(fd, F_GETFL);
} while (flags == -1 && errno == EINTR);

return flags;
}
#endif // __POSIX__


inline void PlatformInit() {
#ifdef __POSIX__
#if HAVE_INSPECTOR
Expand All @@ -3856,16 +3881,18 @@ inline void PlatformInit() {
#endif // HAVE_INSPECTOR

// Make sure file descriptors 0-2 are valid before we start logging anything.
for (int fd = STDIN_FILENO; fd <= STDERR_FILENO; fd += 1) {
struct stat ignored;
if (fstat(fd, &ignored) == 0)
for (auto& s : stdio) {
const int fd = &s - stdio;
if (fstat(fd, &s.stat) == 0)
continue;
// Anything but EBADF means something is seriously wrong. We don't
// have to special-case EINTR, fstat() is not interruptible.
if (errno != EBADF)
ABORT();
if (fd != open("/dev/null", O_RDWR))
ABORT();
if (fstat(fd, &s.stat) != 0)
ABORT();
}

#if HAVE_INSPECTOR
Expand All @@ -3888,6 +3915,24 @@ inline void PlatformInit() {
}
#endif // !NODE_SHARED_MODE

// Record the state of the stdio file descriptors so we can restore it
// on exit. Needs to happen before installing signal handlers because
// they make use of that information.
for (auto& s : stdio) {
const int fd = &s - stdio;
int err;

s.flags = GetFileDescriptorFlags(fd);
CHECK_NE(s.flags, -1);

if (!isatty(fd)) continue;
s.isatty = true;
do {
err = tcgetattr(fd, &s.termios);
} while (err == -1 && errno == EINTR);
CHECK_EQ(err, 0);
}

RegisterSignalHandler(SIGINT, SignalExit, true);
RegisterSignalHandler(SIGTERM, SignalExit, true);

Expand Down Expand Up @@ -3928,6 +3973,49 @@ inline void PlatformInit() {
}


// This function must be safe to call more than once and from signal handlers.
inline void PlatformExit() {
#ifdef __POSIX__
for (auto& s : stdio) {
const int fd = &s - stdio;

struct stat tmp;
if (-1 == fstat(fd, &tmp)) {
CHECK_EQ(errno, EBADF); // Program closed file descriptor.
continue;
}

bool is_same_file =
(s.stat.st_dev == tmp.st_dev && s.stat.st_ino == tmp.st_ino);
if (!is_same_file) continue; // Program reopened file descriptor.

int flags = GetFileDescriptorFlags(fd);
CHECK_NE(flags, -1);

// Restore the O_NONBLOCK flag if it changed.
if (O_NONBLOCK & (flags ^ s.flags)) {
flags &= ~O_NONBLOCK;
flags |= s.flags & O_NONBLOCK;

int err;
do {
err = fcntl(fd, F_SETFL, flags);
} while (err == -1 && errno == EINTR);
CHECK_NE(err, -1);
}

if (s.isatty) {
int err;
do {
err = tcsetattr(fd, TCSANOW, &s.termios);
} while (err == -1 && errno == EINTR);
CHECK_NE(err, -1);
}
}
#endif // __POSIX__
}


void ProcessArgv(int* argc,
const char** argv,
int* exec_argc,
Expand Down Expand Up @@ -4392,7 +4480,7 @@ inline int Start(uv_loop_t* event_loop,
}

int Start(int argc, char** argv) {
atexit([] () { uv_tty_reset_mode(); });
atexit([] () { PlatformExit(); });
PlatformInit();
performance::performance_node_start = PERFORMANCE_NOW();

Expand Down

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