child_spawn*: make sure posix_spawn() doesn't clobber pipes with dup2+close

4 files changed, 37 insertions, 22 deletions

diff --git a/src/libstddjb/child_spawn.c b/src/libstddjb/child_spawn.c
index 964e4e2..58bbfc8 100644
--- a/src/libstddjb/child_spawn.c
+++ b/src/libstddjb/child_spawn.c
@@ -77,14 +77,14 @@ pid_t child_spawn (char const *prog, char const *const *argv, char const *const
   }
   e = posix_spawn_file_actions_init(&actions) ;
   if (e) goto errattr ;
-  if (n >= 2)
+  if (n >= 2 && p[1][0])
   {
     e = posix_spawn_file_actions_adddup2(&actions, p[1][0], 0) ;
     if (e) goto erractions ;
     e = posix_spawn_file_actions_addclose(&actions, p[1][0]) ;
     if (e) goto erractions ;
   }
-  if (n)
+  if (n && p[0][1] != 1)
   {
     e = posix_spawn_file_actions_adddup2(&actions, p[0][1], 1) ;
     if (e) goto erractions ;
diff --git a/src/libstddjb/child_spawn1_internal.c b/src/libstddjb/child_spawn1_internal.c
index 0f9cb16..116a65e 100644
--- a/src/libstddjb/child_spawn1_internal.c
+++ b/src/libstddjb/child_spawn1_internal.c
@@ -32,10 +32,13 @@ pid_t child_spawn1_internal (char const *prog, char const *const *argv, char con
   }
   e = posix_spawn_file_actions_init(&actions) ;
   if (e) goto errattr ;
-  e = posix_spawn_file_actions_adddup2(&actions, p[to & 1], to & 1) ;
-  if (e) goto erractions ;
-  e = posix_spawn_file_actions_addclose(&actions, p[to & 1]) ;
-  if (e) goto erractions ;
+  if (p[to & 1] != to & 1)
+  {
+    e = posix_spawn_file_actions_adddup2(&actions, p[to & 1], to & 1) ;
+    if (e) goto erractions ;
+    e = posix_spawn_file_actions_addclose(&actions, p[to & 1]) ;
+    if (e) goto erractions ;
+  }
   if (to & 2)
   {
     e = posix_spawn_file_actions_adddup2(&actions, to & 1, !(to & 1)) ;
diff --git a/src/libstddjb/child_spawn2.c b/src/libstddjb/child_spawn2.c
index d69764d..4e7d0a5 100644
--- a/src/libstddjb/child_spawn2.c
+++ b/src/libstddjb/child_spawn2.c
@@ -56,14 +56,20 @@ pid_t child_spawn2 (char const *prog, char const *const *argv, char const *const
   }
   e = posix_spawn_file_actions_init(&actions) ;
   if (e) goto errattr ;
-  e = posix_spawn_file_actions_adddup2(&actions, p[1][0], fds[0]) ;
-  if (e) goto erractions ;
-  e = posix_spawn_file_actions_addclose(&actions, p[1][0]) ;
-  if (e) goto erractions ;
-  e = posix_spawn_file_actions_adddup2(&actions, p[0][1], fds[1]) ;
-  if (e) goto erractions ;
-  e = posix_spawn_file_actions_addclose(&actions, p[0][1]) ;
-  if (e) goto erractions ;
+  if (p[1][0] != fds[0])
+  {
+    e = posix_spawn_file_actions_adddup2(&actions, p[1][0], fds[0]) ;
+    if (e) goto erractions ;
+    e = posix_spawn_file_actions_addclose(&actions, p[1][0]) ;
+    if (e) goto erractions ;
+  }
+  if (p[0][1] != fds[1])
+  {
+    e = posix_spawn_file_actions_adddup2(&actions, p[0][1], fds[1]) ;
+    if (e) goto erractions ;
+    e = posix_spawn_file_actions_addclose(&actions, p[0][1]) ;
+    if (e) goto erractions ;
+  }
   {
     int haspath = !!getenv("PATH") ;
     if (!haspath && (setenv("PATH", SKALIBS_DEFAULTPATH, 0) < 0))
diff --git a/src/libstddjb/child_spawn3.c b/src/libstddjb/child_spawn3.c
index 82220ea..9dbed41 100644
--- a/src/libstddjb/child_spawn3.c
+++ b/src/libstddjb/child_spawn3.c
@@ -62,14 +62,20 @@ pid_t child_spawn3 (char const *prog, char const *const *argv, char const *const
   }
   e = posix_spawn_file_actions_init(&actions) ;
   if (e) goto errattr ;
-  e = posix_spawn_file_actions_adddup2(&actions, p[1][0], fds[0]) ;
-  if (e) goto erractions ;
-  e = posix_spawn_file_actions_addclose(&actions, p[1][0]) ;
-  if (e) goto erractions ;
-  e = posix_spawn_file_actions_adddup2(&actions, p[0][1], fds[1]) ;
-  if (e) goto erractions ;
-  e = posix_spawn_file_actions_addclose(&actions, p[0][1]) ;
-  if (e) goto erractions ;
+  if (p[1][0] != fds[0])
+  {
+    e = posix_spawn_file_actions_adddup2(&actions, p[1][0], fds[0]) ;
+    if (e) goto erractions ;
+    e = posix_spawn_file_actions_addclose(&actions, p[1][0]) ;
+    if (e) goto erractions ;
+  }
+  if (p[0][1] != fds[1])
+  {
+    e = posix_spawn_file_actions_adddup2(&actions, p[0][1], fds[1]) ;
+    if (e) goto erractions ;
+    e = posix_spawn_file_actions_addclose(&actions, p[0][1]) ;
+    if (e) goto erractions ;
+  }
   {
     int haspath = !!getenv("PATH") ;
     size_t envlen = env_len(envp) ;