Re: [Xen-devel] [PATCH] EFI: Fix getting EFI variable list on some systems

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 09/03/15 16:47, Ross Lagerwall wrote:
> Copy the entire output buffer to the guest because it may contain data beyond
> the output size that the firmware requires on a subsequent
> GetNextVariableName() call (e.g. a NULL character).
>
> The spec requires that on each call, "the previous results" be passed in.
>
> Without this change, the following (simplified) sequence would occur:
> GetNextVariableName: in \0, out AdminPw\0, size 7
> GetNextVariableName: in AdminPw\0, out UserPw\0, size 6
> GetNextVariableName: in UserPww\0, NOT FOUND
>
> Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

> ---
>  xen/common/efi/runtime.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/xen/common/efi/runtime.c b/xen/common/efi/runtime.c
> index 7ed5bfa..20772f3 100644
> --- a/xen/common/efi/runtime.c
> +++ b/xen/common/efi/runtime.c
> @@ -518,7 +518,7 @@ int efi_runtime_call(struct xenpf_efi_runtime_call *op)
>  
>              if ( !EFI_ERROR(status) &&
>                   copy_to_guest(op->u.get_next_variable_name.name,
> -                               name.raw, size) )
> +                               name.raw, op->u.get_next_variable_name.size) )
>                  rc = -EFAULT;
>              op->u.get_next_variable_name.size = size;
>          }


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