Re: [PATCH 1/1] efi/libstub: tpm: zero initialize pointer variables for mixed mode

[Jarkko Sakkinen]

On Tue, Mar 13, 2018 at 02:09:21PM +, Ard Biesheuvel wrote:
> As reported by Jeremy, running the new TPM libstub code in mixed mode
> (i.e., 64-bit kernel on 32-bit UEFI) results in hangs when invoking
> the TCG2 protocol, or when accessing the log_tbl pool allocation.
> 
> The reason turns out to be that in both cases, the 64-bit pointer
> variables are not fully initialized by the 32-bit EFI code, and so
> we should take care to zero initialize these variables beforehand,
> or we'll end up dereferencing bogus pointers.
> 
> Reported-by: Jeremy Cline 
> Signed-off-by: Ard Biesheuvel 

Reviewed-by: Jarkko Sakkinen 

/Jarkko
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Re: [PATCH 1/1] efi/libstub: tpm: zero initialize pointer variables for mixed mode

[Javier Martinez Canillas]

[adding linux-integrity and tpmdd-devel since this was discussed in these ML 
too]

On 03/13/2018 03:09 PM, Ard Biesheuvel wrote:
> As reported by Jeremy, running the new TPM libstub code in mixed mode
> (i.e., 64-bit kernel on 32-bit UEFI) results in hangs when invoking
> the TCG2 protocol, or when accessing the log_tbl pool allocation.
> 
> The reason turns out to be that in both cases, the 64-bit pointer
> variables are not fully initialized by the 32-bit EFI code, and so
> we should take care to zero initialize these variables beforehand,
> or we'll end up dereferencing bogus pointers.
> 
> Reported-by: Jeremy Cline 
> Signed-off-by: Ard Biesheuvel 
> ---
>  drivers/firmware/efi/libstub/tpm.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/firmware/efi/libstub/tpm.c 
> b/drivers/firmware/efi/libstub/tpm.c
> index da661bf8cb96..13c1edd37e96 100644
> --- a/drivers/firmware/efi/libstub/tpm.c
> +++ b/drivers/firmware/efi/libstub/tpm.c
> @@ -68,11 +68,11 @@ void efi_retrieve_tpm2_eventlog_1_2(efi_system_table_t 
> *sys_table_arg)
>   efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID;
>   efi_status_t status;
>   efi_physical_addr_t log_location, log_last_entry;
> - struct linux_efi_tpm_eventlog *log_tbl;
> + struct linux_efi_tpm_eventlog *log_tbl = NULL;
>   unsigned long first_entry_addr, last_entry_addr;
>   size_t log_size, last_entry_size;
>   efi_bool_t truncated;
> - void *tcg2_protocol;
> + void *tcg2_protocol = NULL;
>  
>   status = efi_call_early(locate_protocol, _guid, NULL,
>   _protocol);
> 

Looks good to me.

Reviewed-by: Javier Martinez Canillas 

Best regards,
-- 
Javier Martinez Canillas
Software Engineer - Desktop Hardware Enablement
Red Hat
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[PATCH 1/1] efi/libstub: tpm: zero initialize pointer variables for mixed mode

[Ard Biesheuvel]

As reported by Jeremy, running the new TPM libstub code in mixed mode
(i.e., 64-bit kernel on 32-bit UEFI) results in hangs when invoking
the TCG2 protocol, or when accessing the log_tbl pool allocation.

The reason turns out to be that in both cases, the 64-bit pointer
variables are not fully initialized by the 32-bit EFI code, and so
we should take care to zero initialize these variables beforehand,
or we'll end up dereferencing bogus pointers.

Reported-by: Jeremy Cline 
Signed-off-by: Ard Biesheuvel 
---
 drivers/firmware/efi/libstub/tpm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/efi/libstub/tpm.c 
b/drivers/firmware/efi/libstub/tpm.c
index da661bf8cb96..13c1edd37e96 100644
--- a/drivers/firmware/efi/libstub/tpm.c
+++ b/drivers/firmware/efi/libstub/tpm.c
@@ -68,11 +68,11 @@ void efi_retrieve_tpm2_eventlog_1_2(efi_system_table_t 
*sys_table_arg)
efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID;
efi_status_t status;
efi_physical_addr_t log_location, log_last_entry;
-   struct linux_efi_tpm_eventlog *log_tbl;
+   struct linux_efi_tpm_eventlog *log_tbl = NULL;
unsigned long first_entry_addr, last_entry_addr;
size_t log_size, last_entry_size;
efi_bool_t truncated;
-   void *tcg2_protocol;
+   void *tcg2_protocol = NULL;
 
status = efi_call_early(locate_protocol, _guid, NULL,
_protocol);
-- 
2.15.1

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