Re: [PATCH v4 01/10] libata: fix ata_host_alloc_pinfo()

[Hannes Reinecke <hare@suse.de>]

On 8/7/21 6:18 AM, Damien Le Moal wrote:
> Avoid static checkers warnings about a potential NULL pointer
> dereference for the port info variable pi. To do so, test that at least
> one port info is available on entry to ata_host_alloc_pinfo() and start
> the ata port initialization for loop with pi initialized to a non-NULL
> pointer. Within the for loop, get the next port info (if it is not NULL)
> after initializing the ata port using the previous port info.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
> ---
>   drivers/ata/libata-core.c | 16 +++++++++++-----
>   1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
> index 61c762961ca8..b17e161c07e2 100644
> --- a/drivers/ata/libata-core.c
> +++ b/drivers/ata/libata-core.c
> @@ -5441,16 +5441,17 @@ struct ata_host *ata_host_alloc_pinfo(struct device *dev,
>   	struct ata_host *host;
>   	int i, j;
>   
> +	/* We must have at least one port info */
> +	if (!ppi[0])
> +		return NULL;
> +
>   	host = ata_host_alloc(dev, n_ports);
>   	if (!host)
>   		return NULL;
>   
> -	for (i = 0, j = 0, pi = NULL; i < host->n_ports; i++) {
> +	for (i = 0, j = 0, pi = ppi[0]; i < host->n_ports; i++) {
>   		struct ata_port *ap = host->ports[i];
>   
> -		if (ppi[j])
> -			pi = ppi[j++];
> -
>   		ap->pio_mask = pi->pio_mask;
>   		ap->mwdma_mask = pi->mwdma_mask;
>   		ap->udma_mask = pi->udma_mask;
> @@ -5458,8 +5459,13 @@ struct ata_host *ata_host_alloc_pinfo(struct device *dev,
>   		ap->link.flags |= pi->link_flags;
>   		ap->ops = pi->port_ops;
>   
> -		if (!host->ops && (pi->port_ops != &ata_dummy_port_ops))
> +		if (!host->ops && pi->port_ops != &ata_dummy_port_ops)
>   			host->ops = pi->port_ops;
> +
> +		if (ppi[j + 1]) {
> +			j++;
> +			pi = ppi[j];
> +		}
>   	}
>   
>   	return host;
> 
This requires a comment as to why this is necessary.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
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