[PATCH] RDMA/mlx5: Prevent UB from shifting negative signed value

[Qasim Ijaz <qasdev00@gmail.com>]

In function create_ib_ah() the following line attempts 
to left shift the return value of mlx5r_ib_rate() by 4 
and store it in the stat_rate_sl member of av:

		ah->av.stat_rate_sl = (mlx5r_ib_rate(dev, rdma_ah_get_static_rate(ah_attr)) << 4);
		
However the code overlooks the fact that mlx5r_ib_rate() 
may return -EINVAL if the rate passed to it is less than 
IB_RATE_2_5_GBPS or greater than IB_RATE_800_GBPS.

Because of this, the code may invoke undefined behaviour when
shifting a signed negative value when doing "-EINVAL << 4".

To fix this check for errors before assigning stat_rate_sl and
propagate any error value to the callers.

Signed-off-by: Qasim Ijaz <qasdev00@gmail.com>
Fixes: c534ffda781f ("RDMA/mlx5: Fix AH static rate parsing")
Cc: stable@vger.kernel.org
---
 drivers/infiniband/hw/mlx5/ah.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/infiniband/hw/mlx5/ah.c b/drivers/infiniband/hw/mlx5/ah.c
index 99036afb3aef..6bccd9ce4538 100644
--- a/drivers/infiniband/hw/mlx5/ah.c
+++ b/drivers/infiniband/hw/mlx5/ah.c
@@ -50,11 +50,12 @@ static __be16 mlx5_ah_get_udp_sport(const struct mlx5_ib_dev *dev,
 	return sport;
 }
 
-static void create_ib_ah(struct mlx5_ib_dev *dev, struct mlx5_ib_ah *ah,
+static int create_ib_ah(struct mlx5_ib_dev *dev, struct mlx5_ib_ah *ah,
 			 struct rdma_ah_init_attr *init_attr)
 {
 	struct rdma_ah_attr *ah_attr = init_attr->ah_attr;
 	enum ib_gid_type gid_type;
+	int rate_val;
 
 	if (rdma_ah_get_ah_flags(ah_attr) & IB_AH_GRH) {
 		const struct ib_global_route *grh = rdma_ah_read_grh(ah_attr);
@@ -67,8 +68,10 @@ static void create_ib_ah(struct mlx5_ib_dev *dev, struct mlx5_ib_ah *ah,
 		ah->av.tclass = grh->traffic_class;
 	}
 
-	ah->av.stat_rate_sl =
-		(mlx5r_ib_rate(dev, rdma_ah_get_static_rate(ah_attr)) << 4);
+	rate_val = mlx5r_ib_rate(dev, rdma_ah_get_static_rate(ah_attr));
+	if (rate_val < 0)
+		return rate_val;
+	ah->av.stat_rate_sl = rate_val << 4;
 
 	if (ah_attr->type == RDMA_AH_ATTR_TYPE_ROCE) {
 		if (init_attr->xmit_slave)
@@ -89,6 +92,8 @@ static void create_ib_ah(struct mlx5_ib_dev *dev, struct mlx5_ib_ah *ah,
 		ah->av.fl_mlid = rdma_ah_get_path_bits(ah_attr) & 0x7f;
 		ah->av.stat_rate_sl |= (rdma_ah_get_sl(ah_attr) & 0xf);
 	}
+
+	return 0;
 }
 
 int mlx5_ib_create_ah(struct ib_ah *ibah, struct rdma_ah_init_attr *init_attr,
@@ -99,6 +104,7 @@ int mlx5_ib_create_ah(struct ib_ah *ibah, struct rdma_ah_init_attr *init_attr,
 	struct mlx5_ib_ah *ah = to_mah(ibah);
 	struct mlx5_ib_dev *dev = to_mdev(ibah->device);
 	enum rdma_ah_attr_type ah_type = ah_attr->type;
+	int ret;
 
 	if ((ah_type == RDMA_AH_ATTR_TYPE_ROCE) &&
 	    !(rdma_ah_get_ah_flags(ah_attr) & IB_AH_GRH))
@@ -121,7 +127,10 @@ int mlx5_ib_create_ah(struct ib_ah *ibah, struct rdma_ah_init_attr *init_attr,
 			return err;
 	}
 
-	create_ib_ah(dev, ah, init_attr);
+	ret = create_ib_ah(dev, ah, init_attr);
+	if (ret)
+		return ret;
+
 	return 0;
 }
 
-- 
2.39.5