linux-kernel - Re: [RFC,PATCH v2] efi: Add support for a UEFI variable filesystem

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Message-ID: <5048B52A.6000602@canonical.com>
Date:	Thu, 06 Sep 2012 22:37:30 +0800
From:	Jeremy Kerr <jeremy.kerr@...onical.com>
To:	Matt Fleming <matt.fleming@...el.com>
CC:	linux-kernel@...r.kernel.org, Matthew Garrett <mjg@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Matt Domsch <Matt_Domsch@...l.com>,
	Peter Jones <pjones@...hat.com>
Subject: Re: [RFC,PATCH v2] efi: Add support for a UEFI variable filesystem

Hi Matt,

> I think this is the problematic chunk of code,
>
> static int efivars_unlink(struct inode *dir, struct dentry *dentry)
> {
>          struct efivar_entry *var = dentry->d_inode->i_private;
>          struct efivars *efivars = var->efivars;
>          efi_status_t status;
>
>          spin_lock(&efivars->lock);
>
>          status = efivars->ops->set_variable(var->var.VariableName,
>                                              &var->var.VendorGuid,
>                                              0, 0, NULL);
>
> For deleting authenticated variables Attributes, DataSize and Data need
> to be non-zero. I think DataSize == AuthInfo descriptor. Peter?

That's correct, but we can't use unlink to delete a secure variable, we 
need to do a write instead, in order to provide the authentication 
descriptor.

But yes, we may need to alter the efivars_file_write path so that such a 
write actually results in the dentry being removed...

Cheers,


Jeremy


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