mlxsw: spectrum_router: Fix error path in mlxsw_sp_vr_create

[ Upstream commit 0f2d2b27 ]

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: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

@@ -729,26 +729,29 @@ static struct mlxsw_sp_fib *mlxsw_sp_vr_fib(const struct mlxsw_sp_vr *vr,
 static struct mlxsw_sp_vr *mlxsw_sp_vr_create(struct mlxsw_sp *mlxsw_sp,
 					      u32 tb_id)
 {
+	struct mlxsw_sp_fib *fib4;
+	struct mlxsw_sp_fib *fib6;
 	struct mlxsw_sp_vr *vr;
 	int err;
 
 	vr = mlxsw_sp_vr_find_unused(mlxsw_sp);
 	if (!vr)
 		return ERR_PTR(-EBUSY);
-	vr->fib4 = mlxsw_sp_fib_create(vr, MLXSW_SP_L3_PROTO_IPV4);
-	if (IS_ERR(vr->fib4))
-		return ERR_CAST(vr->fib4);
-	vr->fib6 = mlxsw_sp_fib_create(vr, MLXSW_SP_L3_PROTO_IPV6);
-	if (IS_ERR(vr->fib6)) {
-		err = PTR_ERR(vr->fib6);
+	fib4 = mlxsw_sp_fib_create(vr, MLXSW_SP_L3_PROTO_IPV4);
+	if (IS_ERR(fib4))
+		return ERR_CAST(fib4);
+	fib6 = mlxsw_sp_fib_create(vr, MLXSW_SP_L3_PROTO_IPV6);
+	if (IS_ERR(fib6)) {
+		err = PTR_ERR(fib6);
 		goto err_fib6_create;
 	}
+	vr->fib4 = fib4;
+	vr->fib6 = fib6;
 	vr->tb_id = tb_id;
 	return vr;
 
 err_fib6_create:
-	mlxsw_sp_fib_destroy(vr->fib4);
-	vr->fib4 = NULL;
+	mlxsw_sp_fib_destroy(fib4);
 	return ERR_PTR(err);
 }