On Thu, 2013-03-07 at 18:34 +0800, joeyli wrote:
> The VariableNameSize is not reliable when EFI_SUCCESS is returned
> because UEFI 2.3.1 spec only mention VariableNameSize should updated
> when EFI_BUFFER_TOO_SMALL is returned. And, the 1024 bytes of buffer is
> from old UEFI spec. There doesn't have any size condition of variable
> data or variable name in 2.3.1 spec.
The spec may only mention what happens in the EFI_BUFFER_TOO_SMALL case,
but for EFI_SUCCESS, any behaviour other than leaving VariableNameSize
alone or updating it with the required size of the buffer is just
completely insane.
> I modified the patch to grab VariableNameSize when EFI_BUFFER_TOO_SMALL,
> the behavior like what we do in efivarfs_file_read().
Thanks, this does seem like the most robust solution.
> This patch works on a normal UEFI machine, we will test it on HP z220. I
> will send out it formally after test success.
Has anyone tried contacting HP to tell them their firmware is doing
bizarre things?
[...]
> @@ -1722,17 +1723,35 @@ int register_efivars(struct efivars *efivars,
> */
>
> do {
> - variable_name_size = 1024;
> + variable_name_size = 0;
>
> status = ops->get_next_variable(&variable_name_size,
> variable_name,
> &vendor_guid);
> switch (status) {
> - case EFI_SUCCESS:
> - efivar_create_sysfs_entry(efivars,
> - variable_name_size,
> - variable_name,
> - &vendor_guid);
> + case EFI_BUFFER_TOO_SMALL:
> + if (variable_name_size < 2) {
> + /* set variable_name_size to buffer size when
> it's too small */
This hunk would be better written like,
if (variable_name_size < sizeof(efi_char16_t) * 2) {
/* Bogus size - expect at least one char + NULL
*/
variable_name_size = variable_name_buff_size;
}
A variable name containing only '\0' is bogus. We need at least one
unicode character + '\0' for a valid variable name.
> + variable_name_size = variable_name_buff_size;
> + } else if (variable_name_size >
> variable_name_buff_size) {
> + /* re-allocate more buffer when size doesn't
> enough */
This comment is redundant. Just delete it.
> + kfree(variable_name);
> + variable_name = kzalloc(variable_name_size,
> GFP_KERNEL);
> + if (!variable_name) {
> + printk(KERN_ERR "efivars: Memory
> allocation failed.\n");
> + return -ENOMEM;
> + }
> + variable_name_buff_size = variable_name_size;
> + }
> + status = ops->get_next_variable(&variable_name_size,
> + variable_name,
> + &vendor_guid);
> + variable_name_size = utf16_strsize(variable_name,
> variable_name_buff_size)+2;
Please document what this +2 represents and why we need it. Better yet,
use sizeof(efi_char16_t), and still document why it's needed, e.g. "Add
terminating NULL".
> + if (status == EFI_SUCCESS)
> + efivar_create_sysfs_entry(efivars,
> + variable_name_size,
> + variable_name,
> + &vendor_guid);
> break;
> case EFI_NOT_FOUND:
> break;
--
Matt Fleming, Intel Open Source Technology Center
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