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Merge pull request #11278 from Mic92/close-fds

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libutil: rename and optimize closeMostFDs
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Robert Hensing 2024-08-26 15:51:34 +02:00 committed by GitHub
commit 8bd835b7bc
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3 changed files with 28 additions and 8 deletions
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2
src/libstore/unix/build/local-derivation-goal.cc
View file

@ -1986,7 +1986,7 @@ void LocalDerivationGoal::runChild()
throw SysError("changing into '%1%'", tmpDir);
/* Close all other file descriptors. */
unix::closeMostFDs({STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO});
unix::closeExtraFDs();
#if __linux__
linux::setPersonality(drv->platform);

4
src/libutil/file-descriptor.hh
View file

@ -154,10 +154,10 @@ public:
namespace unix {
/**
* Close all file descriptors except those listed in the given set.
* Close all file descriptors except stdio fds (ie 0, 1, 2).
* Good practice in child processes.
*/
void closeMostFDs(const std::set<Descriptor> & exceptions);
void closeExtraFDs();
/**
* Set the close-on-exec flag for the given file descriptor.

30
src/libutil/unix/file-descriptor.cc
View file

@ -120,14 +120,35 @@ void Pipe::create()
//////////////////////////////////////////////////////////////////////
void unix::closeMostFDs(const std::set<int> & exceptions)
#if __linux__ || __FreeBSD__
// In future we can use a syscall wrapper, but at the moment musl and older glibc version don't support it.
static int unix_close_range(unsigned int first, unsigned int last, int flags)
{
return syscall(SYS_close_range, first, last, (unsigned int)flags);
}
#endif
void unix::closeExtraFDs()
{
constexpr int MAX_KEPT_FD = 2;
static_assert(std::max({STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO}) == MAX_KEPT_FD);
#if __linux__ || __FreeBSD__
// first try to close_range everything we don't care about. if this
// returns an error with these parameters we're running on a kernel
// that does not implement close_range (i.e. pre 5.9) and fall back
// to the old method. we should remove that though, in some future.
if (unix_close_range(MAX_KEPT_FD + 1, ~0U, 0) == 0) {
return;
}
#endif
#if __linux__
try {
for (auto & s : std::filesystem::directory_iterator{"/proc/self/fd"}) {
checkInterrupt();
auto fd = std::stoi(s.path().filename());
if (!exceptions.count(fd)) {
if (fd > MAX_KEPT_FD) {
debug("closing leaked FD %d", fd);
close(fd);
}
@ -142,9 +163,8 @@ void unix::closeMostFDs(const std::set<int> & exceptions)
#if HAVE_SYSCONF
maxFD = sysconf(_SC_OPEN_MAX);
#endif
for (int fd = 0; fd < maxFD; ++fd)
if (!exceptions.count(fd))
close(fd); /* ignore result */
for (int fd = MAX_KEPT_FD + 1; fd < maxFD; ++fd)
close(fd); /* ignore result */
}