net/mlx4_core: Make sure that negative array index isn't used

To make sure that the array index isn't used in the code with
negative value, we stop using the for loop integer iterator
outside of it.
>From now on use members count to swap the last QP with removed one.
Fix also the second occurrence of this flow in mlx4_qp_detach_common().
In mlx4_qp_detach_common() use members_count instead of
loop iterator outside of the for loop.
Signed-off-by: Dotan Barak <dotanb@dev.mellanox.co.il>
Reviewed-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Signed-off-by: Eugenia Emantayev <eugenia@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/mcg.c

@@ -513,7 +513,7 @@ static int remove_promisc_qp(struct mlx4_dev *dev, u8 port,
 	u32 members_count;
 	bool found;
 	bool back_to_list = false;
-	int loc, i;
+	int i;
 	int err;
 
 	if (port < 1 || port > dev->caps.num_ports)
@@ -565,18 +565,30 @@ static int remove_promisc_qp(struct mlx4_dev *dev, u8 port,
 			list_del(&dqp->list);
 			kfree(dqp);
 		} else {
+			int loc = -1;
 			err = mlx4_READ_ENTRY(dev, entry->index, mailbox);
 				if (err)
 					goto out_mailbox;
 			members_count = be32_to_cpu(mgm->members_count) & 0xffffff;
-			for (loc = -1, i = 0; i < members_count; ++i)
-				if ((be32_to_cpu(mgm->qp[i]) & MGM_QPN_MASK) == qpn)
+			for (i = 0; i < members_count; ++i)
+				if ((be32_to_cpu(mgm->qp[i]) &
+				     MGM_QPN_MASK) == qpn) {
 					loc = i;
+					break;
+				}
+
+			if (loc < 0) {
+				mlx4_err(dev, "QP %06x wasn't found in entry %d\n",
+					 qpn, entry->index);
+				err = -EINVAL;
+				goto out_mailbox;
+			}
 
+			/* copy the last QP in this MGM over removed QP */
+			mgm->qp[loc] = mgm->qp[members_count - 1];
+			mgm->qp[members_count - 1] = 0;
 			mgm->members_count = cpu_to_be32(--members_count |
 							 (MLX4_PROT_ETH << 30));
-			mgm->qp[loc] = mgm->qp[i - 1];
-			mgm->qp[i - 1] = 0;
 
 			err = mlx4_WRITE_ENTRY(dev, entry->index, mailbox);
 				if (err)
@@ -1074,7 +1086,7 @@ int mlx4_qp_detach_common(struct mlx4_dev *dev, struct mlx4_qp *qp, u8 gid[16],
 	struct mlx4_mgm *mgm;
 	u32 members_count;
 	int prev, index;
-	int i, loc;
+	int i, loc = -1;
 	int err;
 	u8 port = gid[5];
 	bool removed_entry = false;
@@ -1103,9 +1115,11 @@ int mlx4_qp_detach_common(struct mlx4_dev *dev, struct mlx4_qp *qp, u8 gid[16],
 		goto out;
 
 	members_count = be32_to_cpu(mgm->members_count) & 0xffffff;
-	for (loc = -1, i = 0; i < members_count; ++i)
-		if ((be32_to_cpu(mgm->qp[i]) & MGM_QPN_MASK) == qp->qpn)
+	for (i = 0; i < members_count; ++i)
+		if ((be32_to_cpu(mgm->qp[i]) & MGM_QPN_MASK) == qp->qpn) {
 			loc = i;
+			break;
+		}
 
 	if (loc == -1) {
 		mlx4_err(dev, "QP %06x not found in MGM\n", qp->qpn);
@@ -1113,15 +1127,15 @@ int mlx4_qp_detach_common(struct mlx4_dev *dev, struct mlx4_qp *qp, u8 gid[16],
 		goto out;
 	}
 
-
+	/* copy the last QP in this MGM over removed QP */
+	mgm->qp[loc] = mgm->qp[members_count - 1];
+	mgm->qp[members_count - 1] = 0;
 	mgm->members_count = cpu_to_be32(--members_count | (u32) prot << 30);
-	mgm->qp[loc]       = mgm->qp[i - 1];
-	mgm->qp[i - 1]     = 0;
 
 	if (prot == MLX4_PROT_ETH)
 		removed_entry = can_remove_steering_entry(dev, port, steer,
 								index, qp->qpn);
-	if (i != 1 && (prot != MLX4_PROT_ETH || !removed_entry)) {
+	if (members_count && (prot != MLX4_PROT_ETH || !removed_entry)) {
 		err = mlx4_WRITE_ENTRY(dev, index, mailbox);
 		goto out;
 	}