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

On 3/4/2025 4:02 PM, Qasim Ijaz wrote:

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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

Thanks for fixing this , looks good to me.

Reviewed-by: Patrisious Haddad phaddad@nvidia.com

---

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