[PATCH] security/integrity: fix pointer to ESL data and its size on pseries

[Jarkko Sakkinen]

On Tue Jun 6, 2023 at 8:26 PM EEST, Nayna Jain wrote:
> On PowerVM guest, variable data is prefixed with 8 bytes of timestamp.
> Extract ESL by stripping off the timestamp before passing to ESL parser.
>

Cc: stable at vger.kenrnel.org # v6.3

?

> Fixes: 4b3e71e9a34c ("integrity/powerpc: Support loading keys from PLPKS")
> Signed-off-by: Nayna Jain <nayna at linux.ibm.com>
> ---
>  .../integrity/platform_certs/load_powerpc.c   | 39 ++++++++++++-------
>  1 file changed, 26 insertions(+), 13 deletions(-)
>
> diff --git a/security/integrity/platform_certs/load_powerpc.c b/security/integrity/platform_certs/load_powerpc.c
> index b9de70b90826..57768cbf1fd3 100644
> --- a/security/integrity/platform_certs/load_powerpc.c
> +++ b/security/integrity/platform_certs/load_powerpc.c
> @@ -15,6 +15,9 @@
>  #include "keyring_handler.h"
>  #include "../integrity.h"
>  
> +#define extract_data(db, data, size, offset)	\
> +	do { db = data + offset; size = size - offset; } while (0)
> +
>  /*
>   * Get a certificate list blob from the named secure variable.
>   *
> @@ -55,8 +58,10 @@ static __init void *get_cert_list(u8 *key, unsigned long keylen, u64 *size)
>   */
>  static int __init load_powerpc_certs(void)
>  {
> +	void *data = NULL;
> +	u64 dsize = 0;
> +	u64 offset = 0;
>  	void *db = NULL, *dbx = NULL;

So... what do you need db still for?

If you meant to rename 'db' to 'data', then you should not do it, since this is
a bug fix. It is zero gain, and a factor harder backport.

> -	u64 dbsize = 0, dbxsize = 0;
>  	int rc = 0;
>  	ssize_t len;
>  	char buf[32];
> @@ -74,38 +79,46 @@ static int __init load_powerpc_certs(void)
>  		return -ENODEV;
>  	}
>  
> +	if (strcmp("ibm,plpks-sb-v1", buf) == 0)
> +		/* PLPKS authenticated variables ESL data is prefixed with 8 bytes of timestamp */
> +		offset = 8;
> +
>  	/*
>  	 * Get db, and dbx. They might not exist, so it isn't an error if we
>  	 * can't get them.
>  	 */
> -	db = get_cert_list("db", 3, &dbsize);
> -	if (!db) {
> +	data = get_cert_list("db", 3, &dsize);
> +	if (!data) {
>  		pr_info("Couldn't get db list from firmware\n");
> -	} else if (IS_ERR(db)) {
> -		rc = PTR_ERR(db);
> +	} else if (IS_ERR(data)) {
> +		rc = PTR_ERR(data);
>  		pr_err("Error reading db from firmware: %d\n", rc);
>  		return rc;
>  	} else {
> -		rc = parse_efi_signature_list("powerpc:db", db, dbsize,
> +		extract_data(db, data, dsize, offset);
> +
> +		rc = parse_efi_signature_list("powerpc:db", db, dsize,
>  					      get_handler_for_db);
>  		if (rc)
>  			pr_err("Couldn't parse db signatures: %d\n", rc);
> -		kfree(db);
> +		kfree(data);
>  	}
>  
> -	dbx = get_cert_list("dbx", 4,  &dbxsize);
> -	if (!dbx) {
> +	data = get_cert_list("dbx", 4,  &dsize);
> +	if (!data) {
>  		pr_info("Couldn't get dbx list from firmware\n");
> -	} else if (IS_ERR(dbx)) {
> -		rc = PTR_ERR(dbx);
> +	} else if (IS_ERR(data)) {
> +		rc = PTR_ERR(data);
>  		pr_err("Error reading dbx from firmware: %d\n", rc);
>  		return rc;
>  	} else {
> -		rc = parse_efi_signature_list("powerpc:dbx", dbx, dbxsize,
> +		extract_data(dbx, data, dsize, offset);
> +
> +		rc = parse_efi_signature_list("powerpc:dbx", dbx, dsize,
>  					      get_handler_for_dbx);
>  		if (rc)
>  			pr_err("Couldn't parse dbx signatures: %d\n", rc);
> -		kfree(dbx);
> +		kfree(data);
>  	}
>  
>  	return rc;
> -- 
> 2.31.1

BR, Jarkko