From: Jiri Pirko <jiri@mellanox.com>
Date: Tue, 13 Feb 2018 11:22:42 +0100
Subject: mlxsw: spectrum_router: Fix error path in mlxsw_sp_vr_create
Git-commit: 0f2d2b2736b08dafa3bde31d048750fbc8df3a31
Patch-mainline: v4.16-rc3
References: networking-stable-18_03_07

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: 76610ebbde18 ("mlxsw: spectrum_router: Refactor virtual router handling")
Fixes: a3d9bc506d64 ("mlxsw: spectrum_router: Extend virtual routers with IPv6 support")
Fixes: d42b0965b1d4 ("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: Jiri Slaby <jslaby@suse.cz>
---
 drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
@@ -595,14 +595,16 @@ static struct mlxsw_sp_fib *mlxsw_sp_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_vr *vr;
 
 	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);
+	fib4 = mlxsw_sp_fib_create(vr, MLXSW_SP_L3_PROTO_IPV4);
+	if (IS_ERR(fib4))
+		return ERR_CAST(fib4);
+	vr->fib4 = fib4;
 	vr->tb_id = tb_id;
 	return vr;
 }