RDMA/uverbs: Restrict usage of privileged QKEYs

According to the IB specification rel-1.6, section 3.5.3:
"QKEYs with the most significant bit set are considered controlled
QKEYs, and a HCA does not allow a consumer to arbitrarily specify a
controlled QKEY."

Thus, block non-privileged users from setting such a QKEY.

Cc: stable@vger.kernel.org
Fixes: bc38a6a ("[PATCH] IB uverbs: core implementation")
Signed-off-by: Edward Srouji <edwards@nvidia.com>
Link: https://lore.kernel.org/r/c00c809ddafaaf87d6f6cb827978670989a511b3.1685960567.git.leon@kernel.org
Signed-off-by: Leon Romanovsky <leon@kernel.org>

Author: EdwardSro

drivers/infiniband/core/uverbs_cmd.c

@@ -1850,8 +1850,13 @@ static int modify_qp(struct uverbs_attr_bundle *attrs,
 		attr->path_mtu = cmd->base.path_mtu;
 	if (cmd->base.attr_mask & IB_QP_PATH_MIG_STATE)
 		attr->path_mig_state = cmd->base.path_mig_state;
-	if (cmd->base.attr_mask & IB_QP_QKEY)
+	if (cmd->base.attr_mask & IB_QP_QKEY) {
+		if (cmd->base.qkey & IB_QP_SET_QKEY && !capable(CAP_NET_RAW)) {
+			ret = -EPERM;
+			goto release_qp;
+		}
 		attr->qkey = cmd->base.qkey;
+	}
 	if (cmd->base.attr_mask & IB_QP_RQ_PSN)
 		attr->rq_psn = cmd->base.rq_psn;
 	if (cmd->base.attr_mask & IB_QP_SQ_PSN)