linux-hardening - Re: [PATCH v2][next] RDMA/core: Use size_{add,mul}() in calls to struct

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Date:   Thu, 14 Sep 2023 20:29:57 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Jason Gunthorpe <jgg@...pe.ca>, Leon Romanovsky <leon@...nel.org>,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2][next] RDMA/core: Use size_{add,mul}() in calls to
 struct_size()

On Mon, Sep 11, 2023 at 05:27:59PM -0600, Gustavo A. R. Silva wrote:
> Harden calls to struct_size() with size_add() and size_mul().

Specifically, make sure that open-coded arithmetic cannot cause an
overflow/wraparound. (i.e. it will stay saturated at SIZE_MAX.)

> 
> Fixes: 467f432a521a ("RDMA/core: Split port and device counter sysfs attributes")
> Fixes: a4676388e2e2 ("RDMA/core: Simplify how the gid_attrs sysfs is created")
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
> Changes in v2:
>  - Update changelog text: remove the part about binary differences (it
>    was added by mistake).
> 
>  drivers/infiniband/core/sysfs.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/infiniband/core/sysfs.c b/drivers/infiniband/core/sysfs.c
> index ee59d7391568..ec5efdc16660 100644
> --- a/drivers/infiniband/core/sysfs.c
> +++ b/drivers/infiniband/core/sysfs.c
> @@ -903,7 +903,7 @@ alloc_hw_stats_device(struct ib_device *ibdev)
>  	 * Two extra attribue elements here, one for the lifespan entry and
>  	 * one to NULL terminate the list for the sysfs core code
>  	 */
> -	data = kzalloc(struct_size(data, attrs, stats->num_counters + 1),
> +	data = kzalloc(struct_size(data, attrs, size_add(stats->num_counters, 1)),
>  		       GFP_KERNEL);
>  	if (!data)
>  		goto err_free_stats;
> @@ -1009,7 +1009,7 @@ alloc_hw_stats_port(struct ib_port *port, struct attribute_group *group)
>  	 * Two extra attribue elements here, one for the lifespan entry and
>  	 * one to NULL terminate the list for the sysfs core code
>  	 */
> -	data = kzalloc(struct_size(data, attrs, stats->num_counters + 1),
> +	data = kzalloc(struct_size(data, attrs, size_add(stats->num_counters, 1)),
>  		       GFP_KERNEL);
>  	if (!data)
>  		goto err_free_stats;
> @@ -1140,7 +1140,7 @@ static int setup_gid_attrs(struct ib_port *port,
>  	int ret;
>  
>  	gid_attr_group = kzalloc(struct_size(gid_attr_group, attrs_list,
> -					     attr->gid_tbl_len * 2),
> +					     size_mul(attr->gid_tbl_len, 2)),
>  				 GFP_KERNEL);
>  	if (!gid_attr_group)
>  		return -ENOMEM;
> @@ -1205,8 +1205,8 @@ static struct ib_port *setup_port(struct ib_core_device *coredev, int port_num,
>  	int ret;
>  
>  	p = kvzalloc(struct_size(p, attrs_list,
> -				attr->gid_tbl_len + attr->pkey_tbl_len),
> -		    GFP_KERNEL);
> +				size_add(attr->gid_tbl_len, attr->pkey_tbl_len)),
> +		     GFP_KERNEL);
>  	if (!p)
>  		return ERR_PTR(-ENOMEM);
>  	p->ibdev = device;
> -- 
> 2.34.1
> 

-- 
Kees Cook