Re: [PATCH] libata: prevent devices with blank model names from being DMA blacklisted

[Jeff Garzik <jeff@garzik.org>]

Andrew Paprocki wrote:
> The strn_pattern_cmp routine does not handle a blank name parameter
> properly. The only patterns which should match a blank name are "*"
> and an explicit "". If the function is passed a blank name in current
> code, it will always match against the patt parameter. The bug manifests
> itself as the device with the empty model name always matching the first
> device in the DMA blacklist, forcing it to revert to PIO mode.
> 
> Signed-off-by: Andrew Paprocki <andrew@ishiboo.com>
> ---
>  drivers/ata/libata-core.c |   13 ++++++++++++-
>  1 files changed, 12 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
> index 4e11e39..e73b7b4 100644
> --- a/drivers/ata/libata-core.c
> +++ b/drivers/ata/libata-core.c
> @@ -4013,8 +4013,19 @@ int strn_pattern_cmp(const char *patt, const
> char *name, int wildchar)
>         p = strchr(patt, wildchar);
>         if (p && ((*(p + 1)) == 0))
>                 len = p - patt;
> -       else
> +       else {
>                 len = strlen(name);
> +               /* If the model name parameter is empty, it should not match
> +                * against anything other than "*" or "".
> +                */
> +               if (unlikely(len == 0)) {
> +                       /* In the rare case your pattern is "". */
> +                       if (strlen(patt) == 0)
> +                               return 0;
> +                       else
> +                               return -1;
> +               }
> +       }

applied manually, patch was corrupted