Re: [PATCH] ata: libata-core: fix NULL pointer deref in ata_host_alloc_pinfo()

[Damien Le Moal <damien.lemoal@opensource.wdc.com>]

On 5/21/22 05:53, Sergey Shtylyov wrote:
> In an unlikely (and probably wrong?) case that the 'ppi' parameter of
> ata_host_alloc_pinfo() points to an array starting with a NULL pointer,
> there's going to be a kernel oops as the 'pi' local variable won't get
> reassigned from the initial value of NULL.  Assign &ata_dummy_port_info
> to 'pi' at the start of the *for* loop instead to fix this kernel oops
> for good...
> 
> Found by Linux Verification Center (linuxtesting.org) with the SVACE static
> analysis tool.
> 
> Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
> 
> ---
> This patch is against the 'for-next' branch of Damien's 'libata.git' repo.
> 
>  drivers/ata/libata-core.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: libata/drivers/ata/libata-core.c
> ===================================================================
> --- libata.orig/drivers/ata/libata-core.c
> +++ libata/drivers/ata/libata-core.c
> @@ -5470,7 +5470,7 @@ struct ata_host *ata_host_alloc_pinfo(st
>  	if (!host)
>  		return NULL;
>  
> -	for (i = 0, j = 0, pi = NULL; i < host->n_ports; i++) {
> +	for (i = 0, j = 0, pi = &ata_dummy_port_info; i < host->n_ports; i++) {
>  		struct ata_port *ap = host->ports[i];
>  
>  		if (ppi[j])

I had a fight with this one a while back as the build bot was complaining
about this a while back. pi cannot be null in this case, but silencing
warnings is good. So OK.

Just one nit: please move the initialization of pi to its declaration to
avoid the overly long for line.

-- 
Damien Le Moal
Western Digital Research