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

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Message-ID: <cf97f6fd-d40a-43f0-8b58-ad51d602fdfd@nvidia.com>
Date: Tue, 4 Mar 2025 17:57:47 +0200
From: Patrisious Haddad <phaddad@...dia.com>
To: Qasim Ijaz <qasdev00@...il.com>, leon@...nel.org, jgg@...pe.ca
Cc: linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org
Subject: Re: [PATCH] RDMA/mlx5: Prevent UB from shifting negative signed value

On 3/4/2025 4:02 PM, Qasim Ijaz wrote:
> External email: Use caution opening links or attachments
>
>
> 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@...il.com>
> Fixes: c534ffda781f ("RDMA/mlx5: Fix AH static rate parsing")
> Cc: stable@...r.kernel.org

Thanks for fixing this , looks good to me.

Reviewed-by: Patrisious Haddad <phaddad@...dia.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
>
>