lock: Do not allow meta-lock count to be more than one

In the current scheme of glusterfs where lock migration is
experimental, (ideally) the rebalance process which is migrating
the file should request for a metalock. Hence, the metalock count
should not be more than one for an inode. In future, if there is a
need for meta-lock from other clients, this patch can be reverted.

Since pl_metalk is called as part of setxattr operation, any client
process(non-rebalance) residing outside trusted network can exhaust
memory of the server node by issuing setxattr repetitively on the
metalock key. The current patch makes sure that more than
one metalock cannot be granted on an inode.

Fixes CVE-2018-14660

updates: bz#1647972
Change-Id: Ie1e697766388718804a9551bc58351808fe71069
Signed-off-by: Susant Palai <spalai@redhat.com>

1 files changed, 34 insertions, 1 deletions

diff --git a/xlators/features/locks/src/posix.c b/xlators/features/locks/src/posix.c
index bf1c97bdbcc..25bbda2072b 100644
--- a/xlators/features/locks/src/posix.c
+++ b/xlators/features/locks/src/posix.c
@@ -2913,6 +2913,39 @@ pl_metalk (call_frame_t *frame, xlator_t *this, inode_t *inode)
                 goto out;
         }
 
+        /* Non rebalance process trying to do metalock */
+        if (frame->root->pid != GF_CLIENT_PID_DEFRAG) {
+            ret = -1;
+            goto out;
+        }
+
+        /* Note: In the current scheme of glusterfs where lock migration is
+         * experimental, (ideally) the rebalance process which is migrating
+         * the file should request for a metalock. Hence, the metalock count
+         * should not be more than one for an inode. In future, if there is a
+         * need for meta-lock from other clients, the following block can be
+         * removed.
+         *
+         * Since pl_metalk is called as part of setxattr operation, any client
+         * process(non-rebalance) residing outside trusted network can exhaust
+         * memory of the server node by issuing setxattr repetitively on the
+         * metalock key. The following code makes sure that more than
+         * one metalock cannot be granted on an inode*/
+        pthread_mutex_lock(&pl_inode->mutex);
+        {
+            if (pl_metalock_is_active(pl_inode)) {
+                gf_msg(this->name, GF_LOG_WARNING, EINVAL, 0,
+                       "More than one meta-lock can not be granted on"
+                    "the inode");
+                ret = -1;
+            }
+        }
+        pthread_mutex_lock(&pl_inode->mutex);
+
+        if (ret == -1) {
+            goto out;
+        }
+
         if (frame->root->client) {
                 ctx = pl_ctx_get (frame->root->client, this);
                 if (!ctx) {
@@ -3092,7 +3125,7 @@ pl_setxattr (call_frame_t *frame, xlator_t *this,
              loc_t *loc, dict_t *dict, int flags, dict_t *xdata)
 {
         int             op_ret          = 0;
-        int             op_errno        = 0;
+        int             op_errno        = EINVAL;
         dict_t          *xdata_rsp      = NULL;
 
         PL_LOCAL_GET_REQUESTS (frame, this, xdata, NULL, loc, NULL);