integrity/powerpc: Improve error handling & reporting when loading certs

A few improvements to load_powerpc.c:

 - include integrity.h for the pr_fmt()
 - move all error reporting out of get_cert_list()
 - use ERR_PTR() to better preserve error detail
 - don't use pr_err() for missing keys

Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230210080401.345462-26-ajd@linux.ibm.com

diff --git a/security/integrity/platform_certs/load_powerpc.c b/security/integrity/platform_certs/load_powerpc.c
index 1e4f80a..dee5160 100644 (file)
--- a/security/integrity/platform_certs/load_powerpc.c
+++ b/security/integrity/platform_certs/load_powerpc.c
@@ -14,9 +14,15 @@
 #include <asm/secure_boot.h>
 #include <asm/secvar.h>
 #include "keyring_handler.h"
+#include "../integrity.h"
 
 /*
  * Get a certificate list blob from the named secure variable.
+ *
+ * Returns:
+ *  - a pointer to a kmalloc'd buffer containing the cert list on success
+ *  - NULL if the key does not exist
+ *  - an ERR_PTR on error
  */
 static __init void *get_cert_list(u8 *key, unsigned long keylen, u64 *size)
 {
@@ -25,19 +31,19 @@ static __init void *get_cert_list(u8 *key, unsigned long keylen, u64 *size)
 
        rc = secvar_ops->get(key, keylen, NULL, size);
        if (rc) {
-               pr_err("Couldn't get size: %d\n", rc);
-               return NULL;
+               if (rc == -ENOENT)
+                       return NULL;
+               return ERR_PTR(rc);
        }
 
        db = kmalloc(*size, GFP_KERNEL);
        if (!db)
-               return NULL;
+               return ERR_PTR(-ENOMEM);
 
        rc = secvar_ops->get(key, keylen, db, size);
        if (rc) {
                kfree(db);
-               pr_err("Error reading %s var: %d\n", key, rc);
-               return NULL;
+               return ERR_PTR(rc);
        }
 
        return db;
@@ -69,7 +75,11 @@ static int __init load_powerpc_certs(void)
         */
        db = get_cert_list("db", 3, &dbsize);
        if (!db) {
-               pr_err("Couldn't get db list from firmware\n");
+               pr_info("Couldn't get db list from firmware\n");
+       } else if (IS_ERR(db)) {
+               rc = PTR_ERR(db);
+               pr_err("Error reading db from firmware: %d\n", rc);
+               return rc;
        } else {
                rc = parse_efi_signature_list("powerpc:db", db, dbsize,
                                              get_handler_for_db);
@@ -81,6 +91,10 @@ static int __init load_powerpc_certs(void)
        dbx = get_cert_list("dbx", 4,  &dbxsize);
        if (!dbx) {
                pr_info("Couldn't get dbx list from firmware\n");
+       } else if (IS_ERR(dbx)) {
+               rc = PTR_ERR(dbx);
+               pr_err("Error reading dbx from firmware: %d\n", rc);
+               return rc;
        } else {
                rc = parse_efi_signature_list("powerpc:dbx", dbx, dbxsize,
                                              get_handler_for_dbx);