Re: [PATCH] infiniband: remove unnecessary null check

[Niels Dossche]

On 8/24/22 10:05, cgel.zte@xxxxxxxxx wrote:
> From: Minghao Chi <chi.minghao@xxxxxxxxxx>
> 
> container_of is never null, so this null check is
> unnecessary.
> 
> Reported-by: Zeal Robot <zealci@xxxxxxxxxx>
> Signed-off-by: Minghao Chi <chi.minghao@xxxxxxxxxx>
> ---
>  drivers/infiniband/sw/rdmavt/vt.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/infiniband/sw/rdmavt/vt.c b/drivers/infiniband/sw/rdmavt/vt.c
> index 59481ae39505..b2d83b4958fc 100644
> --- a/drivers/infiniband/sw/rdmavt/vt.c
> +++ b/drivers/infiniband/sw/rdmavt/vt.c
> @@ -50,8 +50,6 @@ struct rvt_dev_info *rvt_alloc_device(size_t size, int nports)
>  	struct rvt_dev_info *rdi;
>  
>  	rdi = container_of(_ib_alloc_device(size), struct rvt_dev_info, ibdev);
> -	if (!rdi)
> -		return rdi;
>  
>  	rdi->ports = kcalloc(nports, sizeof(*rdi->ports), GFP_KERNEL);
>  	if (!rdi->ports)

I believe this patch is incorrect because "_ib_alloc_device" may return a null pointer.
Note that the first member of "rvt_dev_info" is "ib_device", so the check on container_of effectively checks if the allocation failed, which is necessary to check.