Re: fchdir fixes

[Eric Blake]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

According to Jim Meyering on 12/8/2009 7:51 AM:
> Eric Blake wrote:
>> fchdir is working on mingw, which is about the only modern portability
>> target that lacks fchdir, but it is sure easier to test on other platforms
>> than mingw.
>> Subject: [PATCH 2/2] fchdir: fix logic bugs
> ...
> Good catch.
> The rest looks fine, too.

Another one.  There is a memory leak if you call _gl_register_dup() to the
same target without closing the fd in between.  This is possible at least
in some code paths (such as dup3) when I forced the fchdir replacement
even though the native one works; I did not audit whether mingw was
subject to the leak even though mingw is the only platform likely to be
hit in practice (since most other platforms have fchdir).

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (Cygwin)
Comment: Public key at home.comcast.net/~ericblake/eblake.gpg
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/

iEYEARECAAYFAksfJVcACgkQ84KuGfSFAYCmLgCeNVfLKH2Dv2fO45SVve1cKFcv
coIAoLrcqAvtiuBhrE023W8L4MeAtN3W
=fGuB
-----END PGP SIGNATURE-----

>From aeb9a8a8a97f8b876a378ae4fe330f131437b348 Mon Sep 17 00:00:00 2001
From: Eric Blake <address@hidden>
Date: Tue, 8 Dec 2009 10:23:27 -0700
Subject: [PATCH] fchdir: avoid memory leak on re-registration.

Some code paths (such as dup3) could overwrite one registered
directory fd with another, and must not leak the old name.

* lib/fchdir.c (ensure_dirs_slot): Avoid memory leak.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog    |    5 +++++
 lib/fchdir.c |    9 ++++++---
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 0afec2e..8597a13 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2009-12-08  Eric Blake  <address@hidden>
+
+       fchdir: avoid memory leak on re-registration.
+       * lib/fchdir.c (ensure_dirs_slot): Avoid memory leak.
+
 2009-12-08  Jim Meyering  <address@hidden>

        init.sh: avoid Solaris 10 /bin/sh portability problem
diff --git a/lib/fchdir.c b/lib/fchdir.c
index 4cc0f33..545b207 100644
--- a/lib/fchdir.c
+++ b/lib/fchdir.c
@@ -60,12 +60,15 @@ typedef struct
 static dir_info_t *dirs;
 static size_t dirs_allocated;

-/* Try to ensure dirs has enough room for a slot at index fd.  Return
-   false and set errno to ENOMEM on allocation failure.  */
+/* Try to ensure dirs has enough room for a slot at index fd; free any
+   contents already in that slot.  Return false and set errno to
+   ENOMEM on allocation failure.  */
 static bool
 ensure_dirs_slot (size_t fd)
 {
-  if (fd >= dirs_allocated)
+  if (fd < dirs_allocated)
+    free (dirs[fd].name);
+  else
     {
       size_t new_allocated;
       dir_info_t *new_dirs;
-- 
1.6.5.rc1