2013-03-01 09:32:05

by Lingzhu Xiang

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 <[email protected]>
>
> 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

2013-03-01 14:50:48

by joeyli

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

於 五，2013-03-01 於 17:31 +0800，Lingzhu Xiang 提到：
> On 03/01/2013 11:20 AM, Lee, Chun-Yi wrote:
> > From: Michael Schroeder <[email protected]>
> >
> > 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
>

Yes, it's possible! I will add patch for print more debug messages to
bug reporter for check it.


Thanks for your review!
Joey Lee