[Guile-commits] 01/04: 'spawn' closes only open file descriptors on non-GNU/Linux systems.

[Ludovic Courtès]

civodul pushed a commit to branch main
in repository guile.

commit 21ad54b694c676ba608166be137b677bbb747eac
Author: Ludovic Courtès <ludo@gnu.org>
AuthorDate: Tue Mar 28 23:35:35 2023 +0200

    'spawn' closes only open file descriptors on non-GNU/Linux systems.
    
    Fixes <https://bugs.gnu.org/61095>.
    Reported by Omar Polo <op@omarpolo.com>.
    
    * libguile/posix.c (close_inherited_fds_slow): On systems other than
    GNU/Linux, call 'addclose' only when 'fcntl' succeeds on MAX_FD.
    * NEWS: Update.
---
 NEWS             |  4 +++-
 libguile/posix.c | 19 ++++++++++++++++++-
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/NEWS b/NEWS
index cad53ea03..ce8d4e120 100644
--- a/NEWS
+++ b/NEWS
@@ -24,7 +24,9 @@ the compiler reports it as "possibly unused".
 * Bug fixes
 
 ** (ice-9 suspendable-ports) incorrect UTF-8 decoding
-   (https://bugs.gnu.org/62290)
+   (<https://bugs.gnu.org/62290>)
+** Fix invalid use of 'posix_spawn' on non-glibc systems
+   (<https://bugs.gnu.org/61095>)
 ** Hashing of UTF-8 symbols with non-ASCII characters avoids corruption
    (<https://bugs.gnu.org/56413>)
 
diff --git a/libguile/posix.c b/libguile/posix.c
index 3a8be94e4..68e9bfade 100644
--- a/libguile/posix.c
+++ b/libguile/posix.c
@@ -1326,7 +1326,24 @@ static void
 close_inherited_fds_slow (posix_spawn_file_actions_t *actions, int max_fd)
 {
   while (--max_fd > 2)
-    posix_spawn_file_actions_addclose (actions, max_fd);
+    {
+      /* Adding a 'close' action for a file descriptor that is not open
+         causes 'posix_spawn' to fail on GNU/Hurd and on OpenBSD, but
+         not on GNU/Linux: <https://bugs.gnu.org/61095>.  Hence this
+         strategy:
+
+           - On GNU/Linux, close every FD, since that's the only
+             race-free way to make sure the child doesn't inherit one.
+           - On other systems, only close FDs currently open in the
+             parent; it works, but it's racy (XXX).
+
+         The only reliable option is 'addclosefrom'.  */
+#if ! (defined __GLIBC__ && defined __linux__)
+      int flags = fcntl (max_fd, F_GETFD, NULL);
+      if (flags >= 0)
+#endif
+        posix_spawn_file_actions_addclose (actions, max_fd);
+    }
 }
 
 static void