crytpfs: fix clobbering of crypto info on keymaster failure

Changing the device lock (even from swipe to none) will cause the
master key to be re-encrypted.
If at that point keymaster fails (e.g. due to an incompatible keymaster update)
cryptfs will write back the now-incomplete crypto metadata.
Upon next reboot, userdata can't be decrypted.

Now we don't bother writing on keymaster failure.

Bug: 19301883
Change-Id: I2b9a1278f8b4d333ac8d567e17e2263005e99409

1 files changed, 7 insertions, 4 deletions

diff --git a/cryptfs.c b/cryptfs.c
index d5ceaef..46e6be7 100644
--- a/cryptfs.c
+++ b/cryptfs.c
@@ -3285,6 +3285,7 @@ int cryptfs_enable_default(char *howarg, int allow_reboot)
 int cryptfs_changepw(int crypt_type, const char *newpw)
 {
     struct crypt_mnt_ftr crypt_ftr;
+    int rc;
 
     /* This is only allowed after we've successfully decrypted the master key */
     if (!master_key_saved) {
@@ -3310,18 +3311,20 @@ int cryptfs_changepw(int crypt_type, const char *newpw)
         newpw = adjusted_passwd;
     }
 
-    encrypt_master_key(crypt_type == CRYPT_TYPE_DEFAULT ? DEFAULT_PASSWORD
+    rc = encrypt_master_key(crypt_type == CRYPT_TYPE_DEFAULT ? DEFAULT_PASSWORD
                                                         : newpw,
                        crypt_ftr.salt,
                        saved_master_key,
                        crypt_ftr.master_key,
                        &crypt_ftr);
-
+    free(adjusted_passwd);
+    if (rc) {
+        SLOGE("Encrypt master key failed: %d", rc);
+        return -1;
+    }
     /* save the key */
     put_crypt_ftr_and_key(&crypt_ftr);
 
-    free(adjusted_passwd);
-
 #ifdef CONFIG_HW_DISK_ENCRYPTION
     if (!strcmp((char *)crypt_ftr.crypto_type_name, "aes-xts")) {
         if (crypt_type == CRYPT_TYPE_DEFAULT) {