mlxsw: spectrum_router: Fix error path in mlxsw_sp_vr_create

Since mlxsw_sp_fib_create() and mlxsw_sp_mr_table_create()
use ERR_PTR macro to propagate int err through return of a pointer,
the return value is not NULL in case of failure. So if one
of the calls fails, one of vr->fib4, vr->fib6 or vr->mr4_table
is not NULL and mlxsw_sp_vr_is_used wrongly assumes
that vr is in use which leads to crash like following one:

[ 1293.949291] BUG: unable to handle kernel NULL pointer dereference at 00000000000006c9
[ 1293.952729] IP: mlxsw_sp_mr_table_flush+0x15/0x70 [mlxsw_spectrum]

Fix this by using local variables to hold the pointers and set vr->*
only in case everything went fine.

Fixes: 76610ebb ("mlxsw: spectrum_router: Refactor virtual router handling")
Fixes: a3d9bc50 ("mlxsw: spectrum_router: Extend virtual routers with IPv6 support")
Fixes: d42b0965 ("mlxsw: spectrum_router: Add multicast routes notification handling functionality")
Signed-off-by: NJiri Pirko <jiri@mellanox.com>
Reviewed-by: NIdo Schimmel <idosch@mellanox.com>
Signed-off-by: NJiri Pirko <jiri@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c

@@ -788,6 +788,9 @@ static struct mlxsw_sp_vr *mlxsw_sp_vr_create(struct mlxsw_sp *mlxsw_sp,
 					      u32 tb_id,
 					      struct netlink_ext_ack *extack)
 {
+	struct mlxsw_sp_mr_table *mr4_table;
+	struct mlxsw_sp_fib *fib4;
+	struct mlxsw_sp_fib *fib6;
 	struct mlxsw_sp_vr *vr;
 	int err;
 
@@ -796,29 +799,30 @@ static struct mlxsw_sp_vr *mlxsw_sp_vr_create(struct mlxsw_sp *mlxsw_sp,
 		NL_SET_ERR_MSG(extack, "spectrum: Exceeded number of supported virtual routers");
 		return ERR_PTR(-EBUSY);
 	}
-	vr->fib4 = mlxsw_sp_fib_create(mlxsw_sp, vr, MLXSW_SP_L3_PROTO_IPV4);
-	if (IS_ERR(vr->fib4))
-		return ERR_CAST(vr->fib4);
-	vr->fib6 = mlxsw_sp_fib_create(mlxsw_sp, vr, MLXSW_SP_L3_PROTO_IPV6);
-	if (IS_ERR(vr->fib6)) {
-		err = PTR_ERR(vr->fib6);
+	fib4 = mlxsw_sp_fib_create(mlxsw_sp, vr, MLXSW_SP_L3_PROTO_IPV4);
+	if (IS_ERR(fib4))
+		return ERR_CAST(fib4);
+	fib6 = mlxsw_sp_fib_create(mlxsw_sp, vr, MLXSW_SP_L3_PROTO_IPV6);
+	if (IS_ERR(fib6)) {
+		err = PTR_ERR(fib6);
 		goto err_fib6_create;
 	}
-	vr->mr4_table = mlxsw_sp_mr_table_create(mlxsw_sp, vr->id,
+	mr4_table = mlxsw_sp_mr_table_create(mlxsw_sp, vr->id,
 					     MLXSW_SP_L3_PROTO_IPV4);
-	if (IS_ERR(vr->mr4_table)) {
-		err = PTR_ERR(vr->mr4_table);
+	if (IS_ERR(mr4_table)) {
+		err = PTR_ERR(mr4_table);
 		goto err_mr_table_create;
 	}
+	vr->fib4 = fib4;
+	vr->fib6 = fib6;
+	vr->mr4_table = mr4_table;
 	vr->tb_id = tb_id;
 	return vr;
 
 err_mr_table_create:
-	mlxsw_sp_fib_destroy(mlxsw_sp, vr->fib6);
-	vr->fib6 = NULL;
+	mlxsw_sp_fib_destroy(mlxsw_sp, fib6);
 err_fib6_create:
-	mlxsw_sp_fib_destroy(mlxsw_sp, vr->fib4);
-	vr->fib4 = NULL;
+	mlxsw_sp_fib_destroy(mlxsw_sp, fib4);
 	return ERR_PTR(err);
 }