linux-kernel - Re: [PATCH] efivarfs: fix abnormal GUID in variable name by using strcpy to replace null with dash

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Message-ID: <5130757F.4090702@redhat.com>
Date:	Fri, 01 Mar 2013 17:31:43 +0800
From:	Lingzhu Xiang <lxiang@...hat.com>
To:	"Lee, Chun-Yi" <joeyli.kernel@...il.com>
CC:	matt@...sole-pimps.org, linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org, Michael Schroeder <mls@...e.com>,
	Josh Boyer <jwboyer@...hat.com>,
	Jeremy Kerr <jeremy.kerr@...onical.com>,
	"Lee, Chun-Yi" <jlee@...e.com>
Subject: Re: [PATCH] efivarfs: fix abnormal GUID in variable name by using
 strcpy to replace null with dash

On 03/01/2013 11:20 AM, Lee, Chun-Yi wrote:
> From: Michael Schroeder <mls@...e.com>
> 
> On HP z220 system (firmware version 1.54), some EFI variables are incorrectly
> named :
> 
> ls -d /sys/firmware/efi/vars/*8be4d* | grep -v -- -8be returns
> /sys/firmware/efi/vars/dbxDefault-pport8be4df61-93ca-11d2-aa0d-00e098032b8c
> /sys/firmware/efi/vars/KEKDefault-pport8be4df61-93ca-11d2-aa0d-00e098032b8c
> /sys/firmware/efi/vars/SecureBoot-pport8be4df61-93ca-11d2-aa0d-00e098032b8c
> /sys/firmware/efi/vars/SetupMode-Information8be4df61-93ca-11d2-aa0d-00e098032b8c
> 
> That causes by the following statement in efivar_create_sysfs_entry function:
> 
>   *(short_name + strlen(short_name)) = '-';
> efi_guid_unparse(vendor_guid, short_name + strlen(short_name));
> 
> The trailing \0 is overwritten with '-', but the next char doesn't seem to be a \0
> as well for HP. So, the second strlen return the point of next '\0', causes there
> have garbage string attached before GUID.
> 
> Tested on On HP z220.

So short_name has trailing garbage, or rather, variable_name_size
is larger than variable_name actually is, wouldn't new_efivar->var.VariableName
also gets filled with trailing garbage?

In efivar_store_raw the VariableName's trailing garbage can cause
problem for comparison. You might want to also cover that or fix
variable_name_size.


Lingzhu Xiang
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