diff options
Diffstat (limited to 'butl')
| -rw-r--r-- | butl/fdstream | 20 | ||||
| -rw-r--r-- | butl/fdstream.cxx | 23 | ||||
| -rw-r--r-- | butl/process.cxx | 2 |
3 files changed, 42 insertions, 3 deletions
diff --git a/butl/fdstream b/butl/fdstream index 8d01b2f..8d6385f 100644 --- a/butl/fdstream +++ b/butl/fdstream @@ -486,6 +486,9 @@ namespace butl // process' umask, so effective permissions are permissions & ~umask. On // Windows permissions other than ru and wu are unlikelly to have effect. // + // Also note that on POSIX the FD_CLOEXEC flag is set for the file descriptor + // to prevent its leakage into child processes. + // LIBBUTL_EXPORT auto_fd fdopen (const char*, fdopen_mode, @@ -510,6 +513,13 @@ namespace butl // Duplicate an open file descriptor. Throw ios::failure on the underlying // OS error. // + // Note that on POSIX the FD_CLOEXEC flag is set for the new descriptor if it + // is present for the source one. That's in contrast to POSIX dup() that + // doesn't copy file descriptor flags. Also note that duplicating descriptor + // and setting the flag is not an atomic operation. + // + // @@ Should we copy HANDLE_FLAG_INHERIT flag on Windows as well? + // LIBBUTL_EXPORT auto_fd fddup (int fd); @@ -563,6 +573,9 @@ namespace butl // closed. One difference, however, would be if you were to both write to // and read from the descriptor. // + // Note that on POSIX the FD_CLOEXEC flag is set for the file descriptor to + // prevent its leakage into child processes. + // // @@ You may have noticed that this interface doesn't match fdopen() (it // does not throw and return int instead of auto_fd). The reason for this // is process and its need to translate everything to process_error). @@ -591,6 +604,13 @@ namespace butl // In particular, the process class that uses fdpipe underneath makes the // appropriate end of pipe (the one being passed to the child) inheritable. // + // Note that on POSIX the FD_CLOEXEC flag is set for both ends, so they get + // automatically closed by the child process to prevent undesired behaviors + // (such as child deadlock on read from a pipe due to the write-end leakage + // into the child process). Opening pipe and setting the flag is not an + // atomic operation. Also note that you don't need to reset the flag for a + // pipe end being passed to the process class ctor. + // LIBBUTL_EXPORT fdpipe fdopen_pipe (fdopen_mode = fdopen_mode::none); } diff --git a/butl/fdstream.cxx b/butl/fdstream.cxx index 370a75e..e28eb0f 100644 --- a/butl/fdstream.cxx +++ b/butl/fdstream.cxx @@ -658,7 +658,7 @@ namespace butl of |= O_LARGEFILE; #endif - int fd (open (f, of, pf)); + int fd (open (f, of | O_CLOEXEC, pf)); #else @@ -745,6 +745,18 @@ namespace butl { #ifndef _WIN32 int nfd (dup (fd)); + + int f (fcntl (fd, F_GETFD)); + if (f == -1) + throw_ios_failure (errno); + + if ((f & FD_CLOEXEC) != 0) + { + f = fcntl (nfd, F_GETFD); + if (f == -1 || fcntl (nfd, F_SETFD, f | FD_CLOEXEC) == -1) + throw_ios_failure (errno); + } + #else int nfd (_dup (fd)); #endif @@ -766,7 +778,7 @@ namespace butl int fdnull () noexcept { - return open ("/dev/null", O_RDWR); + return open ("/dev/null", O_RDWR | O_CLOEXEC); } fdstream_mode @@ -829,6 +841,13 @@ namespace butl if (pipe (pd) == -1) throw_ios_failure (errno); + for (size_t i (0); i < 2; ++i) + { + int f (fcntl (pd[i], F_GETFD)); + if (f == -1 || fcntl (pd[i], F_SETFD, f | FD_CLOEXEC) == -1) + throw_ios_failure (errno); + } + return {auto_fd (pd[0]), auto_fd (pd[1])}; } diff --git a/butl/process.cxx b/butl/process.cxx index 526966e..892e930 100644 --- a/butl/process.cxx +++ b/butl/process.cxx @@ -865,7 +865,7 @@ namespace butl // Resolve file descriptor to HANDLE and make sure it is inherited. Note // that the handle is closed either when CloseHandle() is called for it or // when _close() is called for the associated file descriptor. Make sure - // that either the original file descriptor or the resulted HANDLE is + // that either the original file descriptor or the resulting HANDLE is // closed but not both of them. // auto get_osfhandle = [&fail](int fd) -> HANDLE |