[gnome-keyring] Fix issue found by address sanitizer

[Stefan Walter <stefw src gnome org>]

commit 760f60931a13c6c422a09dca47eb8cb69898d0ec
Author: Milan Crha <mcrha redhat com>
Date:   Thu Aug 6 12:04:00 2015 +0000

    Fix issue found by address sanitizer
    
    There was done a read of one item more than the array was allocated.
    This patch fixes the issue.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=752919

 pkcs11/rpc-layer/gkm-rpc-util.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/pkcs11/rpc-layer/gkm-rpc-util.c b/pkcs11/rpc-layer/gkm-rpc-util.c
index 340baf7..e7d5a61 100644
--- a/pkcs11/rpc-layer/gkm-rpc-util.c
+++ b/pkcs11/rpc-layer/gkm-rpc-util.c
@@ -81,9 +81,10 @@ gkm_rpc_mechanism_list_purge (CK_MECHANISM_TYPE_PTR mechs, CK_ULONG* n_mechs)
        for (i = 0; i < (int)(*n_mechs); ++i) {
                if (!gkm_rpc_mechanism_has_no_parameters (mechs[i]) &&
                    !gkm_rpc_mechanism_has_sane_parameters (mechs[i])) {
-
-                       /* Remove the mechanism from the list */
-                       memmove (&mechs[i], &mechs[i + 1], (*n_mechs - i) * sizeof (CK_MECHANISM_TYPE));
+                       if (*n_mechs - i - 1 > 0) {
+                               /* Remove the mechanism from the list */
+                               memmove (&mechs[i], &mechs[i + 1], (*n_mechs - i - 1) * sizeof 
(CK_MECHANISM_TYPE));
+                       }
 
                        --(*n_mechs);
                        --i;