Re: [Xen-devel] [PATCH] xen/pciback: Fix conf_space read/write overlap check.

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 21/06/16 15:37, Andrey Grodzovsky wrote:
> Current overlap check is evaluating to false a case where a filter field
> is fully contained (proper subset) of a r/w request.
> This change applies classical overlap check instead to include
> all the scenarios.

Reviewed-by: David Vrabel <david.vrabel@xxxxxxxxxx>

But the commit message could do with a concrete example of an access
that failed.

David

> 
> Related to https://www.mail-archive.com/xen-devel@xxxxxxxxxxxxx/msg72174.html
> 
> Cc: Jan Beulich <JBeulich@xxxxxxxx>
> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Andrey Grodzovsky <andrey2805@xxxxxxxxx>
> ---
>  drivers/xen/xen-pciback/conf_space.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/xen/xen-pciback/conf_space.c 
> b/drivers/xen/xen-pciback/conf_space.c
> index 8e67336..6a25533 100644
> --- a/drivers/xen/xen-pciback/conf_space.c
> +++ b/drivers/xen/xen-pciback/conf_space.c
> @@ -183,8 +183,7 @@ int xen_pcibk_config_read(struct pci_dev *dev, int 
> offset, int size,
>               field_start = OFFSET(cfg_entry);
>               field_end = OFFSET(cfg_entry) + field->size;
>  
> -             if ((req_start >= field_start && req_start < field_end)
> -                 || (req_end > field_start && req_end <= field_end)) {
> +              if (req_end > field_start && field_end > req_start) {
>                       err = conf_space_read(dev, cfg_entry, field_start,
>                                             &tmp_val);
>                       if (err)
> @@ -230,8 +229,7 @@ int xen_pcibk_config_write(struct pci_dev *dev, int 
> offset, int size, u32 value)
>               field_start = OFFSET(cfg_entry);
>               field_end = OFFSET(cfg_entry) + field->size;
>  
> -             if ((req_start >= field_start && req_start < field_end)
> -                 || (req_end > field_start && req_end <= field_end)) {
> +              if (req_end > field_start && field_end > req_start) {
>                       tmp_val = 0;
>  
>                       err = xen_pcibk_config_read(dev, field_start,
> 


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