On Mon, Aug 12, 2019 at 08:06:44PM -0400, Theodore Y. Ts'o wrote:

quoted

+		/* Some inodes still reference this key; try to evict them. */
+		if (try_to_lock_encrypted_files(sb, mk) != 0)
+			status_flags |=
+				FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY;
+	}

try_to_lock_encrypted_files() can return other errors besides -EBUSY;
in particular sync_filesystem() can return other errors, such as -EIO
or -EFSCORUPTED.  In that case, I think we're better off returning the
relevant status code back to the user.  We will have already wiped the
master key, but this situation will only happen in exceptional
conditions (e.g., user has ejected the sdcard, etc.), so it's not
worth it to try to undo the master key wipe to try to restore things
to the pre-ioctl execution state.

So I think we should capture the return code from
try_to_lock_encrypted_files, and if it is EBUSY, we can set FILES_BUSY
flag and return success.  Otherwise, we should return the error.

If you agree, please fix that up and then feel free to add:

Reviewed-by: Theodore Ts'o <tytso@mit.edu>

						- Ted

Yes, that makes sense.  I've made the following change to this patch:

diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c
index 9901593051424b..c3423f0edc7014 100644
--- a/fs/crypto/keyring.c
+++ b/fs/crypto/keyring.c

@@ -479,6 +479,7 @@ int fscrypt_ioctl_remove_key(struct file *filp, void __user *_uarg)
 	struct key *key;
 	struct fscrypt_master_key *mk;
 	u32 status_flags = 0;
+	int err;
 	bool dead;
 
 	if (copy_from_user(&arg, uarg, sizeof(arg)))

@@ -514,11 +515,15 @@ int fscrypt_ioctl_remove_key(struct file *filp, void __user *_uarg)
 		 * key object is free to be removed from the keyring.
 		 */
 		key_invalidate(key);
+		err = 0;
 	} else {
 		/* Some inodes still reference this key; try to evict them. */
-		if (try_to_lock_encrypted_files(sb, mk) != 0)
+		err = try_to_lock_encrypted_files(sb, mk);
+		if (err == -EBUSY) {
 			status_flags |=
 				FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY;
+			err = 0;
+		}
 	}
 	/*
 	 * We return 0 if we successfully did something: wiped the secret, or

@@ -527,7 +532,9 @@ int fscrypt_ioctl_remove_key(struct file *filp, void __user *_uarg)
 	 * including all files locked.
 	 */
 	key_put(key);
-	return put_user(status_flags, &uarg->removal_status_flags);
+	if (err == 0)
+		err = put_user(status_flags, &uarg->removal_status_flags);
+	return err;
 }
 EXPORT_SYMBOL_GPL(fscrypt_ioctl_remove_key);