| /* Invoke popen, but avoid some glitches. |
| |
| Copyright (C) 2009-2020 Free Software Foundation, Inc. |
| |
| This program is free software: you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 3 of the License, or |
| (at your option) any later version. |
| |
| This program is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with this program. If not, see <https://www.gnu.org/licenses/>. */ |
| |
| /* Written by Eric Blake. */ |
| |
| #include <config.h> |
| |
| #include "stdio-safer.h" |
| |
| #include <errno.h> |
| #include <fcntl.h> |
| #include <unistd.h> |
| |
| /* Like popen, but do not return stdin, stdout, or stderr. */ |
| |
| FILE * |
| popen_safer (char const *cmd, char const *mode) |
| { |
| /* Unfortunately, we cannot use the fopen_safer approach of using |
| fdopen (dup_safer (fileno (popen (cmd, mode)))), because stdio |
| libraries maintain hidden state tying the original fd to the pid |
| to wait on when using pclose (this hidden state is also used to |
| avoid fd leaks in subsequent popen calls). So, we instead |
| guarantee that all standard streams are open prior to the popen |
| call (even though this puts more pressure on open fds), so that |
| the original fd created by popen is safe. */ |
| FILE *fp; |
| int fd = open ("/dev/null", O_RDONLY | O_CLOEXEC); |
| if (0 <= fd && fd <= STDERR_FILENO) |
| { |
| /* Maximum recursion depth is 3. */ |
| int saved_errno; |
| fp = popen_safer (cmd, mode); |
| saved_errno = errno; |
| close (fd); |
| errno = saved_errno; |
| } |
| else |
| { |
| /* Either all fd's are tied up, or fd is safe and the real popen |
| will reuse it. */ |
| close (fd); |
| fp = popen (cmd, mode); |
| } |
| return fp; |
| } |