posix_spawn_file_actions_addopen needs to copy the path argument (BZ 17048)

POSIX requires that we make a copy, so we allocate a new string
and free it in posix_spawn_file_actions_destroy.

Reported by David Reid, Alex Gaynor, and Glyph Lefkowitz.  This bug
may have security implications.

6 files changed, 54 insertions, 8 deletions

diff --git a/ChangeLog b/ChangeLog
index d86e739..3020b9a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+2014-06-11  Florian Weimer  <fweimer@redhat.com>
+
+	[BZ #17048]
+	* posix/spawn_int.h (struct __spawn_action): Make the path string
+	non-const to support deallocation.
+	* posix/spawn_faction_addopen.c
+	(posix_spawn_file_actions_addopen): Make a copy of the pathname.
+	* posix/spawn_faction_destroy.c
+	(posix_spawn_file_actions_destroy): Adjust comment.  Deallocate
+	path in all spawn_do_open actions.
+	* posix/tst-spawn.c (do_test): Exercise the copy operation in
+	posix_spawn_file_actions_addopen.
+
 2014-06-11  Chris Metcalf  <cmetcalf@tilera.com>
 
 	* sysdeps/unix/sysv/linux/tile/pt-vfork.c: New file.
diff --git a/NEWS b/NEWS
index ca3ef63..655226d 100644
--- a/NEWS
+++ b/NEWS
@@ -19,7 +19,7 @@ Version 2.20
   16791, 16796, 16799, 16800, 16815, 16823, 16824, 16831, 16838, 16849,
   16854, 16876, 16877, 16878, 16882, 16885, 16888, 16890, 16912, 16915,
   16916, 16917, 16922, 16927, 16928, 16932, 16943, 16958, 16965, 16966,
-  16967, 16977, 16978, 16984, 16990, 17009, 17042.
+  16967, 16977, 16978, 16984, 16990, 17009, 17042, 17048.
 
 * The minimum Linux kernel version that this version of the GNU C Library
   can be used with is 2.6.32.
diff --git a/posix/spawn_faction_addopen.c b/posix/spawn_faction_addopen.c
index 47f6242..40800b8 100644
--- a/posix/spawn_faction_addopen.c
+++ b/posix/spawn_faction_addopen.c
@@ -35,17 +35,24 @@ posix_spawn_file_actions_addopen (posix_spawn_file_actions_t *file_actions,
   if (fd < 0 || fd >= maxfd)
     return EBADF;
 
+  char *path_copy = strdup (path);
+  if (path_copy == NULL)
+    return ENOMEM;
+
   /* Allocate more memory if needed.  */
   if (file_actions->__used == file_actions->__allocated
       && __posix_spawn_file_actions_realloc (file_actions) != 0)
-    /* This can only mean we ran out of memory.  */
-    return ENOMEM;
+    {
+      /* This can only mean we ran out of memory.  */
+      free (path_copy);
+      return ENOMEM;
+    }
 
   /* Add the new value.  */
   rec = &file_actions->__actions[file_actions->__used];
   rec->tag = spawn_do_open;
   rec->action.open_action.fd = fd;
-  rec->action.open_action.path = path;
+  rec->action.open_action.path = path_copy;
   rec->action.open_action.oflag = oflag;
   rec->action.open_action.mode = mode;
 
diff --git a/posix/spawn_faction_destroy.c b/posix/spawn_faction_destroy.c
index 4d165aa..1b87010 100644
--- a/posix/spawn_faction_destroy.c
+++ b/posix/spawn_faction_destroy.c
@@ -18,11 +18,29 @@
 #include <spawn.h>
 #include <stdlib.h>
 
-/* Initialize data structure for file attribute for `spawn' call.  */
+#include "spawn_int.h"
+
+/* Deallocate the file actions.  */
 int
 posix_spawn_file_actions_destroy (posix_spawn_file_actions_t *file_actions)
 {
-  /* Free the memory allocated.  */
+  /* Free the paths in the open actions.  */
+  for (int i = 0; i < file_actions->__used; ++i)
+    {
+      struct __spawn_action *sa = &file_actions->__actions[i];
+      switch (sa->tag)
+	{
+	case spawn_do_open:
+	  free (sa->action.open_action.path);
+	  break;
+	case spawn_do_close:
+	case spawn_do_dup2:
+	  /* No cleanup required.  */
+	  break;
+	}
+    }
+
+  /* Free the array of actions.  */
   free (file_actions->__actions);
   return 0;
 }
diff --git a/posix/spawn_int.h b/posix/spawn_int.h
index 5609e58..861e3b4 100644
--- a/posix/spawn_int.h
+++ b/posix/spawn_int.h
@@ -22,7 +22,7 @@ struct __spawn_action
     struct
     {
       int fd;
-      const char *path;
+      char *path;
       int oflag;
       mode_t mode;
     } open_action;
diff --git a/posix/tst-spawn.c b/posix/tst-spawn.c
index 84cecf2..6cd874a 100644
--- a/posix/tst-spawn.c
+++ b/posix/tst-spawn.c
@@ -168,6 +168,7 @@ do_test (int argc, char *argv[])
   char fd2name[18];
   char fd3name[18];
   char fd4name[18];
+  char *name3_copy;
   char *spargv[12];
   int i;
 
@@ -222,9 +223,15 @@ do_test (int argc, char *argv[])
    if (posix_spawn_file_actions_addclose (&actions, fd1) != 0)
      error (EXIT_FAILURE, errno, "posix_spawn_file_actions_addclose");
    /* We want to open the third file.  */
-   if (posix_spawn_file_actions_addopen (&actions, fd3, name3,
+   name3_copy = strdup (name3);
+   if (name3_copy == NULL)
+     error (EXIT_FAILURE, errno, "strdup");
+   if (posix_spawn_file_actions_addopen (&actions, fd3, name3_copy,
 					 O_RDONLY, 0666) != 0)
      error (EXIT_FAILURE, errno, "posix_spawn_file_actions_addopen");
+   /* Overwrite the name to check that a copy has been made.  */
+   memset (name3_copy, 'X', strlen (name3_copy));
+
    /* We dup the second descriptor.  */
    fd4 = MAX (2, MAX (fd1, MAX (fd2, fd3))) + 1;
    if (posix_spawn_file_actions_adddup2 (&actions, fd2, fd4) != 0)
@@ -253,6 +260,7 @@ do_test (int argc, char *argv[])
    /* Cleanup.  */
    if (posix_spawn_file_actions_destroy (&actions) != 0)
      error (EXIT_FAILURE, errno, "posix_spawn_file_actions_destroy");
+   free (name3_copy);
 
   /* Wait for the child.  */
   if (waitpid (pid, &status, 0) != pid)