Libguestfs - Jan 2012 - [PATCH 00/14] Run the daemon under valgrind and fix resultant errors.

This patch series lets you run the daemon under valgrind.

Many errors were found and fixed.

With the complete series applied, valgrind doesn't show any errors.

From: "Richard W.M. Jones" <rjones at redhat.com>

This commit allows you to run the daemon under valgrind.  You have to
enable it at configure time:

  ./configure --enable-valgrind-daemon

This should *not* be done for production builds.

When this feature is enabled, valgrind is added to the appliance and
the daemon is run under valgrind.  Log messages from valgrind are
passed back over a virtio-serial channel into a file called
'valgrind.log.$PID' in the top build directory.

Running 'make check', 'make extra-tests' etc causes many
valgrind.log.* files to be created which must be examined by hand.
---
 .gitignore               |    1 +
 appliance/Makefile.am    |    9 +++++++--
 appliance/init           |   10 +++++++++-
 appliance/packagelist.in |    4 ++++
 configure.ac             |   15 +++++++++++++++
 src/guestfs.c            |    8 ++++++++
 src/launch.c             |   10 ++++++++++
 7 files changed, 54 insertions(+), 3 deletions(-)

diff --git a/.gitignore b/.gitignore
index b75cafb..fc732bc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -387,3 +387,4 @@ test-tool/libguestfs-test-tool-helper
 tools/test.img
 tools/virt-*.1
 tools/virt-*.pl
+/valgrind.log.*
diff --git a/appliance/Makefile.am b/appliance/Makefile.am
index e2e8b96..99896be 100644
--- a/appliance/Makefile.am
+++ b/appliance/Makefile.am
@@ -42,13 +42,18 @@ make.sh: make.sh.in
 	chmod +x $@-t
 	mv $@-t $@
 
+PACKAGELIST_CPP_FLAGS = -D$(DISTRO)=1
+if VALGRIND_DAEMON
+PACKAGELIST_CPP_FLAGS += -DVALGRIND_DAEMON=1
+endif
+
 packagelist: packagelist.in
-	cpp -undef -D$(DISTRO)=1 < $< | \
+	cpp -undef $(PACKAGELIST_CPP_FLAGS) < $< | \
 	grep -v '^[[:space:]]*$$' | grep -v '^#' > $@-t
 	mv $@-t $@
 
 excludelist: excludelist.in
-	cpp -undef -D$(DISTRO)=1 < $< | \
+	cpp -undef $(PACKAGELIST_CPP_FLAGS) < $< | \
 	grep -v '^[[:space:]]*$$' | grep -v '^#' > $@-t
 	mv $@-t $@
 
diff --git a/appliance/init b/appliance/init
index 0f32a55..1d69339 100755
--- a/appliance/init
+++ b/appliance/init
@@ -106,8 +106,16 @@ if grep -sq guestfs_verbose=1 /proc/cmdline; then
 fi
 
 if ! grep -sq guestfs_rescue=1 /proc/cmdline; then
+  # Run the daemon under valgrind if ./configure --enable-valgrind-daemon
+  vg_channel=/dev/virtio-ports/org.libguestfs.valgrind
+  if [ -w $vg_channel ]; then
+    exec 3>$vg_channel
+    vg="valgrind --leak-check=full --log-fd=3 --error-exitcode=119
--max-stackframe=8388608 --child-silent-after-fork=yes"
+    echo "enabling valgrind: $vg"
+  fi
+
   # The host will kill qemu abruptly if guestfsd shuts down normally
-  guestfsd
+  $vg guestfsd
 
   # Otherwise we try to clean up gracefully. For example, this ensures that a
   # core dump generated by the guest daemon will be written to disk.
diff --git a/appliance/packagelist.in b/appliance/packagelist.in
index 5735a5a..b42c510 100644
--- a/appliance/packagelist.in
+++ b/appliance/packagelist.in
@@ -130,3 +130,7 @@ tar
 xfsprogs
 #endif
 zerofree
+
+#ifdef VALGRIND_DAEMON
+valgrind
+#endif
diff --git a/configure.ac b/configure.ac
index 3e364b1..ebc20aa 100644
--- a/configure.ac
+++ b/configure.ac
@@ -264,8 +264,23 @@ if test "x$enable_daemon" = "xyes";
then
                 [],
                 [enable_install_daemon=no])
         AC_MSG_RESULT([$enable_install_daemon])
+
+        dnl Enable valgrind in the daemon.
+        AC_MSG_CHECKING([if we should run the daemon under valgrind])
+        AC_ARG_ENABLE([valgrind-daemon],
+                [AS_HELP_STRING([--enable-valgrind-daemon],
+                  [run the daemon under valgrind (developers only)
@<:@default=no@:>@])],
+                  [],
+                  [enable_valgrind_daemon=no])
+        AC_MSG_RESULT([$enable_valgrind_daemon])
+
+        if test "x$enable_valgrind_daemon" = "xyes"; then
+            AC_DEFINE([VALGRIND_DAEMON],[1],[Define to 1 to run the daemon
under valgrind])
+            AC_DEFINE_UNQUOTED([VALGRIND_LOG_PATH],["$(pwd)"],[Path
to save valgrind log files])
+        fi
 fi
 AM_CONDITIONAL([INSTALL_DAEMON],[test "x$enable_install_daemon" =
"xyes"])
+AM_CONDITIONAL([VALGRIND_DAEMON],[test "x$enable_valgrind_daemon" =
"xyes"])
 
 dnl Build the appliance?
 AC_MSG_CHECKING([if we should build the appliance])
diff --git a/src/guestfs.c b/src/guestfs.c
index 31968e4..3607eaa 100644
--- a/src/guestfs.c
+++ b/src/guestfs.c
@@ -190,9 +190,17 @@ guestfs_close (guestfs_h *g)
   if (g->autosync && g->state == READY)
     guestfs_internal_autosync (g);
 
+  /* If we are valgrinding the daemon, then we *don't* want to kill
+   * the subprocess because we want the final valgrind messages sent
+   * when we close sockets below.  However for normal production use,
+   * killing the subprocess is the right thing to do (in case the
+   * daemon or qemu is not responding).
+   */
+#ifndef VALGRIND_DAEMON
   /* Kill the qemu subprocess. */
   if (g->state != CONFIG)
     guestfs_kill_subprocess (g);
+#endif
 
   /* Run user close callbacks. */
   guestfs___call_callbacks_void (g, GUESTFS_EVENT_CLOSE);
diff --git a/src/launch.c b/src/launch.c
index 1af74b9..4e2fba9 100644
--- a/src/launch.c
+++ b/src/launch.c
@@ -703,6 +703,16 @@ launch_appliance (guestfs_h *g)
     add_cmdline (g, "-device");
     add_cmdline (g,
"virtserialport,chardev=channel0,name=org.libguestfs.channel.0");
 
+#ifdef VALGRIND_DAEMON
+    /* Set up virtio-serial channel for valgrind messages. */
+    add_cmdline (g, "-chardev");
+    snprintf (buf, sizeof buf,
"file,path=%s/valgrind.log.%d,id=valgrind",
+              VALGRIND_LOG_PATH, getpid ());
+    add_cmdline (g, buf);
+    add_cmdline (g, "-device");
+    add_cmdline (g,
"virtserialport,chardev=valgrind,name=org.libguestfs.valgrind");
+#endif
+
     /* Enable user networking. */
     if (g->enable_network) {
       add_cmdline (g, "-netdev");
-- 
1.7.6

From: "Richard W.M. Jones" <rjones at redhat.com>

---
 daemon/initrd.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/daemon/initrd.c b/daemon/initrd.c
index 7c4d03f..d9c7050 100644
--- a/daemon/initrd.c
+++ b/daemon/initrd.c
@@ -108,9 +108,11 @@ do_initrd_cat (const char *path, const char *filename,
size_t *size_r)
   int r = system (cmd);
   if (r == -1) {
     reply_with_perror ("command failed: %s", cmd);
+    free (cmd);
     rmdir (tmpdir);
     return NULL;
   }
+  free (cmd);
   if (WEXITSTATUS (r) != 0) {
     reply_with_perror ("command failed with return code %d",
                        WEXITSTATUS (r));
-- 
1.7.6

From: "Richard W.M. Jones" <rjones at redhat.com>

This uninitialized data was also sent over the protocol,
potentially being a serious information leak.
---
 daemon/proto.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/daemon/proto.c b/daemon/proto.c
index bf0d75f..4ca2b70 100644
--- a/daemon/proto.c
+++ b/daemon/proto.c
@@ -263,6 +263,7 @@ send_error (int errnum, const char *msg)
 
   xdrmem_create (&xdr, buf, sizeof buf, XDR_ENCODE);
 
+  memset (&hdr, 0, sizeof hdr);
   hdr.prog = GUESTFS_PROGRAM;
   hdr.vers = GUESTFS_PROTOCOL_VERSION;
   hdr.direction = GUESTFS_DIRECTION_REPLY;
@@ -315,6 +316,7 @@ reply (xdrproc_t xdrp, char *ret)
 
   xdrmem_create (&xdr, buf, sizeof buf, XDR_ENCODE);
 
+  memset (&hdr, 0, sizeof hdr);
   hdr.prog = GUESTFS_PROGRAM;
   hdr.vers = GUESTFS_PROTOCOL_VERSION;
   hdr.direction = GUESTFS_DIRECTION_REPLY;
-- 
1.7.6

From: "Richard W.M. Jones" <rjones at redhat.com>

---
 daemon/proto.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/daemon/proto.c b/daemon/proto.c
index 4ca2b70..ac62a6b 100644
--- a/daemon/proto.c
+++ b/daemon/proto.c
@@ -312,7 +312,7 @@ reply (xdrproc_t xdrp, char *ret)
   char buf[GUESTFS_MESSAGE_MAX];
   char lenbuf[4];
   struct guestfs_message_header hdr;
-  unsigned len;
+  uint32_t len;
 
   xdrmem_create (&xdr, buf, sizeof buf, XDR_ENCODE);
 
@@ -352,7 +352,7 @@ reply (xdrproc_t xdrp, char *ret)
     fprintf (stderr, "guestfsd: xwrite failed\n");
     exit (EXIT_FAILURE);
   }
-  if (xwrite (sock, buf, len) == -1) {
+  if (xwrite (sock, buf, (size_t) len) == -1) {
     fprintf (stderr, "guestfsd: xwrite failed\n");
     exit (EXIT_FAILURE);
   }
-- 
1.7.6

From: "Richard W.M. Jones" <rjones at redhat.com>

---
 daemon/guestfsd.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/daemon/guestfsd.c b/daemon/guestfsd.c
index ad260a3..a28e090 100644
--- a/daemon/guestfsd.c
+++ b/daemon/guestfsd.c
@@ -203,6 +203,8 @@ main (int argc, char *argv[])
       printf ("could not read linux command line\n");
   }
 
+  free (cmdline);
+
 #ifndef WIN32
   /* Make sure SIGPIPE doesn't kill us. */
   struct sigaction sa;
-- 
1.7.6

From: "Richard W.M. Jones" <rjones at redhat.com>

---
 daemon/guestfsd.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/daemon/guestfsd.c b/daemon/guestfsd.c
index a28e090..721c169 100644
--- a/daemon/guestfsd.c
+++ b/daemon/guestfsd.c
@@ -377,7 +377,7 @@ sysroot_path (const char *path)
 int
 xwrite (int sock, const void *v_buf, size_t len)
 {
-  int r;
+  ssize_t r;
   const char *buf = v_buf;
 
   while (len > 0) {
-- 
1.7.6

From: "Richard W.M. Jones" <rjones at redhat.com>

This is just a code clean-up with no functional change.
---
 daemon/blkid.c |   39 +++++++++++++++++++++------------------
 1 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/daemon/blkid.c b/daemon/blkid.c
index 3126f85..ada2d7b 100644
--- a/daemon/blkid.c
+++ b/daemon/blkid.c
@@ -129,23 +129,24 @@ test_blkid_p_i_opt (void)
 static char **
 blkid_with_p_i_opt (const char *device)
 {
+  size_t i;
   int r;
   char *out = NULL, *err = NULL;
   char **lines = NULL;
   char **ret = NULL;
   int size = 0, alloc = 0;
 
-  r = command(&out, &err, "blkid", "-c",
"/dev/null",
+  r = command (&out, &err, "blkid", "-c",
"/dev/null",
                "-p", "-i", "-o",
"export", device, NULL);
   if (r == -1) {
-    reply_with_error("%s", err);
+    reply_with_error ("%s", err);
     goto error;
   }
 
   /* Split the command output into lines */
-  lines = split_lines(out);
+  lines = split_lines (out);
   if (lines == NULL) {
-    reply_with_perror("malloc");
+    reply_with_perror ("malloc");
     goto error;
   }
 
@@ -164,38 +165,40 @@ blkid_with_p_i_opt (const char *device)
    * PART_ENTRY_SIZE=104857600
    * PART_ENTRY_DISK=8:0
    */
-  for (char **i = lines; *i != NULL; i++) {
-    char *line = *i;
+  for (i = 0; lines[i] != NULL; ++i) {
+    char *line = lines[i];
 
     /* Skip blank lines (shouldn't happen) */
     if (line[0] == '\0') continue;
 
     /* Split the line in 2 at the equals sign */
-    char *eq = strchr(line, '=');
+    char *eq = strchr (line, '=');
     if (eq) {
       *eq = '\0'; eq++;
 
       /* Add the key/value pair to the output */
-      if (add_string(&ret, &size, &alloc, line) == -1 ||
-          add_string(&ret, &size, &alloc, eq) == -1) goto error;
+      if (add_string (&ret, &size, &alloc, line) == -1 ||
+          add_string (&ret, &size, &alloc, eq) == -1) goto error;
     } else {
-      fprintf(stderr, "blkid: unexpected blkid output ignored: %s",
line);
+      fprintf (stderr, "blkid: unexpected blkid output ignored: %s",
line);
     }
   }
 
-  if (add_string(&ret, &size, &alloc, NULL) == -1) goto error;
+  if (add_string (&ret, &size, &alloc, NULL) == -1) goto error;
 
-  free(out);
-  free(err);
-  free(lines);
+  free (out);
+  free (err);
+  free (lines);
 
   return ret;
 
 error:
-  free(out);
-  free(err);
-  if (lines) free(lines);
-  if (ret) free_strings(ret);
+  free (out);
+  free (err);
+  if (lines)
+    free (lines);
+  if (ret)
+    free_strings (ret);
 
   return NULL;
 }
-- 
1.7.6

From: "Richard W.M. Jones" <rjones at redhat.com>

---
 daemon/blkid.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/daemon/blkid.c b/daemon/blkid.c
index ada2d7b..8728c29 100644
--- a/daemon/blkid.c
+++ b/daemon/blkid.c
@@ -188,7 +188,7 @@ blkid_with_p_i_opt (const char *device)
 
   free (out);
   free (err);
-  free (lines);
+  free_strings (lines);
 
   return ret;
 
@@ -196,7 +196,7 @@ error:
   free (out);
   free (err);
   if (lines)
-    free (lines);
+    free_strings (lines);
   if (ret)
     free_strings (ret);
 
-- 
1.7.6

From: "Richard W.M. Jones" <rjones at redhat.com>

This is just a code clean-up with no functional change.
---
 daemon/md.c |   43 +++++++++++++++++++++++--------------------
 1 files changed, 23 insertions(+), 20 deletions(-)

diff --git a/daemon/md.c b/daemon/md.c
index 5a4d815..fea3cf4 100644
--- a/daemon/md.c
+++ b/daemon/md.c
@@ -235,6 +235,7 @@ error:
 char **
 do_md_detail(const char *md)
 {
+  size_t i;
   int r;
 
   char *out = NULL, *err = NULL;
@@ -244,16 +245,16 @@ do_md_detail(const char *md)
   int size = 0, alloc = 0;
 
   const char *mdadm[] = { "mdadm", "-D",
"--export", md, NULL };
-  r = commandv(&out, &err, mdadm);
+  r = commandv (&out, &err, mdadm);
   if (r == -1) {
-    reply_with_error("%s", err);
+    reply_with_error ("%s", err);
     goto error;
   }
 
   /* Split the command output into lines */
-  lines = split_lines(out);
+  lines = split_lines (out);
   if (lines == NULL) {
-    reply_with_perror("malloc");
+    reply_with_perror ("malloc");
     goto error;
   }
 
@@ -264,49 +265,51 @@ do_md_detail(const char *md)
    * MD_UUID=cfa81b59:b6cfbd53:3f02085b:58f4a2e1
    * MD_NAME=localhost.localdomain:0
    */
-  for (char **i = lines; *i != NULL; i++) {
-    char *line = *i;
+  for (i = 0; lines[i] != NULL; ++i) {
+    char *line = lines[i];
 
     /* Skip blank lines (shouldn't happen) */
     if (line[0] == '\0') continue;
 
     /* Split the line in 2 at the equals sign */
-    char *eq = strchr(line, '=');
+    char *eq = strchr (line, '=');
     if (eq) {
       *eq = '\0'; eq++;
 
       /* Remove the MD_ prefix from the key and translate the remainder to
lower
        * case */
-      if (STRPREFIX(line, "MD_")) {
+      if (STRPREFIX (line, "MD_")) {
         line += 3;
         for (char *j = line; *j != '\0'; j++) {
-          *j = c_tolower(*j);
+          *j = c_tolower (*j);
         }
       }
 
       /* Add the key/value pair to the output */
-      if (add_string(&ret, &size, &alloc, line) == -1 ||
-          add_string(&ret, &size, &alloc, eq) == -1) goto error;
+      if (add_string (&ret, &size, &alloc, line) == -1 ||
+          add_string (&ret, &size, &alloc, eq) == -1) goto error;
     } else {
       /* Ignore lines with no equals sign (shouldn't happen). Log to stderr
so
        * it will show up in LIBGUESTFS_DEBUG. */
-      fprintf(stderr, "md-detail: unexpected mdadm output ignored:
%s", line);
+      fprintf (stderr, "md-detail: unexpected mdadm output ignored:
%s", line);
     }
   }
 
-  free(out);
-  free(err);
-  free(lines); /* We freed the contained strings when we freed out */
+  free (out);
+  free (err);
+  free (lines); /* We freed the contained strings when we freed out */
 
-  if (add_string(&ret, &size, &alloc, NULL) == -1) return NULL;
+  if (add_string (&ret, &size, &alloc, NULL) == -1) return NULL;
 
   return ret;
 
 error:
-  free(out);
-  free(err);
-  if (lines) free(lines);
-  if (ret) free_strings(ret);
+  free (out);
+  free (err);
+  if (lines)
+    free (lines);
+  if (ret)
+    free_strings (ret);
 
   return NULL;
 }
-- 
1.7.6

From: "Richard W.M. Jones" <rjones at redhat.com>

---
 daemon/md.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/daemon/md.c b/daemon/md.c
index fea3cf4..f6dc603 100644
--- a/daemon/md.c
+++ b/daemon/md.c
@@ -297,7 +297,7 @@ do_md_detail(const char *md)
 
   free (out);
   free (err);
-  free (lines); /* We freed the contained strings when we freed out */
+  free_strings (lines);
 
   if (add_string (&ret, &size, &alloc, NULL) == -1) return NULL;
 
@@ -307,7 +307,7 @@ error:
   free (out);
   free (err);
   if (lines)
-    free (lines);
+    free_strings (lines);
   if (ret)
     free_strings (ret);
 
-- 
1.7.6

From: "Richard W.M. Jones" <rjones at redhat.com>

---
 daemon/augeas.c |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/daemon/augeas.c b/daemon/augeas.c
index 03cba42..83d24ad 100644
--- a/daemon/augeas.c
+++ b/daemon/augeas.c
@@ -38,6 +38,17 @@
  */
 static augeas *aug = NULL;
 
+/* Clean up the augeas handle on daemon exit. */
+static void aug_finalize (void) __attribute__((destructor));
+static void
+aug_finalize (void)
+{
+  if (aug) {
+    aug_close (aug);
+    aug = NULL;
+  }
+}
+
 #define NEED_AUG(errcode)						\
   do {									\
     if (!aug) {								\
-- 
1.7.6

From: "Richard W.M. Jones" <rjones at redhat.com>

---
 daemon/inotify.c |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/daemon/inotify.c b/daemon/inotify.c
index e7ce423..add1f14 100644
--- a/daemon/inotify.c
+++ b/daemon/inotify.c
@@ -40,6 +40,17 @@ static int inotify_fd = -1;
 static char inotify_buf[64*1024*1024];	/* Event buffer, [0..posn-1] is valid */
 static size_t inotify_posn = 0;
 
+/* Clean up the inotify handle on daemon exit. */
+static void inotify_finalize (void) __attribute__((destructor));
+static void
+inotify_finalize (void)
+{
+  if (inotify_fd >= 0) {
+    close (inotify_fd);
+    inotify_fd = -1;
+  }
+}
+
 int
 optgroup_inotify_available (void)
 {
-- 
1.7.6

From: "Richard W.M. Jones" <rjones at redhat.com>

---
 daemon/md.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/daemon/md.c b/daemon/md.c
index f6dc603..41e2c75 100644
--- a/daemon/md.c
+++ b/daemon/md.c
@@ -327,5 +327,6 @@ do_md_stop(const char *md)
     free(err);
     return -1;
   }
+  free (err);
   return 0;
 }
-- 
1.7.6

From: "Richard W.M. Jones" <rjones at redhat.com>

This commit tidies up the code by splitting out the path
element-searching code into a separate function.

Valgrind found that 'closedir' frees the 'struct dirent *',
which
wasn't immediately obvious.  So now we do the 'closedir' after all
operations which touch 'd->d_name'.
---
 daemon/realpath.c |  119 ++++++++++++++++++++++++++++++++++++-----------------
 1 files changed, 81 insertions(+), 38 deletions(-)

diff --git a/daemon/realpath.c b/daemon/realpath.c
index c58fc6c..8ec9674 100644
--- a/daemon/realpath.c
+++ b/daemon/realpath.c
@@ -66,6 +66,8 @@ do_realpath (const char *path)
 #endif
 }
 
+static int find_path_element (int fd_cwd, char *name, size_t *name_len_ret);
+
 char *
 do_case_sensitive_path (const char *path)
 {
@@ -110,57 +112,26 @@ do_case_sensitive_path (const char *path)
     path += i;
 
     /* Read the current directory looking (case insensitively) for
-     * this element of the path.
+     * this element of the path.  This replaces 'name' with the
+     * correct case version.
      */
-    int fd2 = dup (fd_cwd); /* because closedir will close it */
-    if (fd2 == -1) {
-      reply_with_perror ("dup");
-      goto error;
-    }
-    DIR *dir = fdopendir (fd2);
-    if (dir == NULL) {
-      reply_with_perror ("opendir");
-      goto error;
-    }
-
-    struct dirent *d = NULL;
-
-    errno = 0;
-    while ((d = readdir (dir)) != NULL) {
-      if (STRCASEEQ (d->d_name, name))
-        break;
-    }
-
-    if (d == NULL && errno != 0) {
-      reply_with_perror ("readdir");
+    if (find_path_element (fd_cwd, name, &i) == -1)
       goto error;
-    }
-
-    if (closedir (dir) == -1) {
-      reply_with_perror ("closedir");
-      goto error;
-    }
-
-    if (d == NULL) {
-      reply_with_error ("%s: no file or directory found with this
name", name);
-      goto error;
-    }
 
     /* Add the real name of this path element to the return value. */
     if (next > 1)
       ret[next++] = '/';
 
-    i = strlen (d->d_name);
     if (next + i >= PATH_MAX) {
       reply_with_error ("final path too long");
       goto error;
     }
 
-    strcpy (&ret[next], d->d_name);
+    strcpy (&ret[next], name);
     next += i;
 
     /* Is it a directory?  Try going into it. */
-    fd2 = openat (fd_cwd, d->d_name, O_RDONLY | O_DIRECTORY);
+    int fd2 = openat (fd_cwd, name, O_RDONLY | O_DIRECTORY);
     int err = errno;
     close (fd_cwd);
     fd_cwd = fd2;
@@ -168,12 +139,12 @@ do_case_sensitive_path (const char *path)
     if (fd_cwd == -1) {
       /* ENOTDIR is OK provided we've reached the end of the path. */
       if (errno != ENOTDIR) {
-        reply_with_perror ("openat: %s", d->d_name);
+        reply_with_perror ("openat: %s", name);
         goto error;
       }
 
       if (*path) {
-        reply_with_error ("%s: non-directory element in path",
d->d_name);
+        reply_with_error ("%s: non-directory element in path", name);
         goto error;
       }
     }
@@ -196,3 +167,75 @@ do_case_sensitive_path (const char *path)
 
   return NULL;
 }
+
+/* 'fd_cwd' is a file descriptor pointing to an open directory.
+ * 'name' is a buffer of NAME_MAX+1 characters in size which initially
+ * contains the path element to search for.
+ *
+ * We search the directory looking for a path element that case
+ * insensitively matches 'name' and update the 'name' buffer.
+ *
+ * If this is successful, return 0.  If it fails, reply with an error
+ * and return -1.
+ */
+static int
+find_path_element (int fd_cwd, char *name, size_t *name_len_ret)
+{
+  int fd2;
+  DIR *dir;
+  struct dirent *d;
+
+  fd2 = dup (fd_cwd); /* because closedir will close it */
+  if (fd2 == -1) {
+    reply_with_perror ("dup");
+    return -1;
+  }
+  dir = fdopendir (fd2);
+  if (dir == NULL) {
+    reply_with_perror ("opendir");
+    close (fd2);
+    return -1;
+  }
+
+  for (;;) {
+    errno = 0;
+    d = readdir (dir);
+    if (d == NULL)
+      break;
+    if (STRCASEEQ (d->d_name, name))
+      break;
+  }
+
+  if (d == NULL && errno != 0) {
+    reply_with_perror ("readdir");
+    closedir (dir);
+    return -1;
+  }
+
+  if (d == NULL) {
+    reply_with_error ("%s: no file or directory found with this
name", name);
+    closedir (dir);
+    return -1;
+  }
+
+  *name_len_ret = strlen (d->d_name);
+  if (*name_len_ret > NAME_MAX) {
+    /* Should never happen? */
+    reply_with_error ("path element longer than NAME_MAX");
+    closedir (dir);
+    return -1;
+  }
+
+  /* Safe because name is a buffer of NAME_MAX+1 characters. */
+  strcpy (name, d->d_name);
+
+  /* NB: closedir frees the structure associated with 'd', so we must
+   * do this last.
+   */
+  if (closedir (dir) == -1) {
+    reply_with_perror ("closedir");
+    return -1;
+  }
+
+  return 0;
+}
-- 
1.7.6