[PATCH] posix: Handle negative fds in spawn's addfchdir

[Lucas Chollet]

Hello all,
This is my first contribution here, so I hope I got everything right.
I tested this patch on my Linux x86_64 machine with `make check` and
got no regressions compared to master.

8<

This patch makes `posix_spawn_file_actions_addfchdir` return EBADF on
negative file descriptors. This is mandated by POSIX and similar to what
is already done in addopen/addclose.

Signed-off-by: Lucas Chollet <lucas.chollet@free.fr>
---
 posix/spawn_faction_addfchdir.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/posix/spawn_faction_addfchdir.c b/posix/spawn_faction_addfchdir.c
index a3df6df489..b51139a61f 100644
--- a/posix/spawn_faction_addfchdir.c
+++ b/posix/spawn_faction_addfchdir.c
@@ -28,6 +28,9 @@ posix_spawn_file_actions_addfchdir_np (posix_spawn_file_actions_t *actions,
 {
   struct __spawn_action *rec;
 
+  if (!__spawn_valid_fd (fd))
+    return EBADF;
+
   /* Allocate more memory if needed.  */
   if (actions->__used == actions->__allocated
       && __posix_spawn_file_actions_realloc (actions) != 0)
-- 
2.51.0