Re: [PATCH] efi: reserve memory for tpm_log only if TPM final events table is valid

[Usama Arif <usamaarif642@gmail.com>]

On 30/08/2024 17:42, Gregory Price wrote:
> On Fri, Aug 30, 2024 at 10:28:52PM +0100, Usama Arif wrote:
>> If efi.tpm_log is corrupted, log_tbl->size can be garbage (and
>> negative). This can result in a large memblock reservation, resulting
>> in the kernel booting without sufficient memory. Move the memblock
>> reservation after log_tbl->version check, and check the value of
>> both tbl_size and memblock_reserve.
>>
>> Signed-off-by: Usama Arif <usamaarif642@gmail.com>
>> ---
>>  drivers/firmware/efi/tpm.c | 16 +++++++++++++---
>>  1 file changed, 13 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/firmware/efi/tpm.c b/drivers/firmware/efi/tpm.c
>> index e8d69bd548f3..cfc6a065f441 100644
>> --- a/drivers/firmware/efi/tpm.c
>> +++ b/drivers/firmware/efi/tpm.c
>> @@ -59,9 +59,6 @@ int __init efi_tpm_eventlog_init(void)
>>  		return -ENOMEM;
>>  	}
>>  
>> -	tbl_size = sizeof(*log_tbl) + log_tbl->size;
>> -	memblock_reserve(efi.tpm_log, tbl_size);
>> -
>>  	if (efi.tpm_final_log == EFI_INVALID_TABLE_ADDR) {
>>  		pr_info("TPM Final Events table not present\n");
>>  		goto out;
> 
> The final event table is not present in TCG 1_2 format, but the
> tpm log still needs to be mapped.  So this change is incorrect for
> v1_2.

hmm so we have 

	if (efi.tpm_final_log == EFI_INVALID_TABLE_ADDR) {
		pr_info("TPM Final Events table not present\n");
		goto out;
	} else if (log_tbl->version != EFI_TCG2_EVENT_LOG_FORMAT_TCG_2) {
		pr_warn(FW_BUG "TPM Final Events table invalid\n");
		goto out;
	}

If the format is TCG 1_2, then log_tbl is not used?


> 
>> @@ -70,6 +67,19 @@ int __init efi_tpm_eventlog_init(void)
>>  		goto out;
>>  	}
>>  
>> +	tbl_size = sizeof(*log_tbl) + log_tbl->size;
>> +	if (tbl_size < 0) {
>> +		pr_err(FW_BUG "Failed to parse event in TPM Final Events Log\n");
>> +		ret = -EINVAL;
>> +		goto out;
>> +	}
>> +	if (memblock_reserve(efi.tpm_log, tbl_size)) {
>> +		pr_err("TPM Event Log memblock reserve fails 0x%lx - %x\n",
>> +		       efi.tpm_log, tbl_size);
>> +		ret = -ENOMEM;
>> +		goto out;
>> +	}
>> +
>>  	final_tbl = early_memremap(efi.tpm_final_log, sizeof(*final_tbl));
>>  
>>  	if (!final_tbl) {
>> -- 
>> 2.43.5
>>