gvfschannel: Return proper error if we're out of free fds

In case of too many open files within the process the
g_vfs_channel_init() call fails on socketpair and subsequent
g_vfs_channel_steal_remote_fd() call returns -1 for the fd.
Then g_unix_fd_list_append() hits the assert and doesn't set an
error we're dereferencing afterwards.

This patch doesn't solve the lack of free fds situation and since glib
heavily depends on it it would fail somewhere else. We're just fixing
the segfault and returning nicer error.

Based on a fix suggested by Stephen M. Webb

https://bugzilla.gnome.org/show_bug.cgi?id=696713

1 files changed, 11 insertions, 1 deletions

diff --git a/daemon/gvfsjobopenforread.c b/daemon/gvfsjobopenforread.c
index 32eaf59e..d9781365 100644
--- a/daemon/gvfsjobopenforread.c
+++ b/daemon/gvfsjobopenforread.c
@@ -174,7 +174,17 @@ create_reply (GVfsJob *job,
                                     open_job->pid);
 
   remote_fd = g_vfs_channel_steal_remote_fd (G_VFS_CHANNEL (channel));
-  
+  if (remote_fd < 0)
+    {
+      /* expecting we're out of fds when remote_fd == -1 */
+      g_dbus_method_invocation_return_error_literal (invocation,
+                                                     G_IO_ERROR,
+                                                     G_IO_ERROR_TOO_MANY_OPEN_FILES,
+                                                     _("Couldn't get stream file descriptor"));
+      g_object_unref (channel);
+      return;
+    }
+
   fd_list = g_unix_fd_list_new ();
   error = NULL;
   fd_id = g_unix_fd_list_append (fd_list, remote_fd, &error);