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

[Gregory Price <gourry@gourry.net>]

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.

> @@ -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
>