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src: remap invalid file descriptors using dup2 #44461

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Oct 26, 2022
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src: remap invalid file descriptors using dup2 #44461

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25 changes: 23 additions & 2 deletions src/node.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -608,11 +608,32 @@ static void PlatformInit(ProcessInitializationFlags::Flags flags) {
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 EBADF (file descriptor doesn't exist), open /dev/null and duplicate
// its file descriptor to the invalid file descriptor. Make sure *that*
// file descriptor is valid. POSIX doesn't guarantee the next file
// descriptor open(2) gives us is the lowest available number anymore in
// POSIX.1-2017, which is why dup2(2) is needed.
int null_fd;

do {
null_fd = open("/dev/null", O_RDWR);
} while (null_fd < 0 && errno == EINTR);

if (null_fd != fd) {
int err;

do {
err = dup2(null_fd, fd);
} while (err < 0 && errno == EINTR);
CHECK_EQ(err, 0);
}

if (fstat(fd, &s.stat) < 0) ABORT();
}
}

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