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From: Eric Biggers <ebiggers@kernel.org>
To: "Theodore Y. Ts'o" <tytso@mit.edu>
Cc: Satya Tangirala <satyat@google.com>,
	linux-api@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net,
	linux-fscrypt@vger.kernel.org, keyrings@vger.kernel.org,
	linux-mtd@lists.infradead.org, linux-crypto@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, Jaegeuk Kim <jaegeuk@kernel.org>,
	linux-ext4@vger.kernel.org, Paul Crowley <paulcrowley@google.com>
Subject: Re: [PATCH v8 10/20] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl
Date: Wed, 14 Aug 2019 15:35:43 -0700
Message-ID: <20190814223542.GE101319@gmail.com> (raw)
In-Reply-To: <20190813000644.GH28705@mit.edu>

On Mon, Aug 12, 2019 at 08:06:44PM -0400, Theodore Y. Ts'o wrote:
> > +		/* 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);
 

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Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-05 16:25 [PATCH v8 00/20] fscrypt: key management improvements Eric Biggers
2019-08-05 16:25 ` [PATCH v8 01/20] fs, fscrypt: move uapi definitions to new header <linux/fscrypt.h> Eric Biggers
2019-08-05 16:25 ` [PATCH v8 02/20] fscrypt: use FSCRYPT_ prefix for uapi constants Eric Biggers
2019-08-05 16:25 ` [PATCH v8 03/20] fscrypt: use FSCRYPT_* definitions, not FS_* Eric Biggers
2019-08-05 16:25 ` [PATCH v8 04/20] fscrypt: add ->ci_inode to fscrypt_info Eric Biggers
2019-08-05 16:25 ` [PATCH v8 05/20] fscrypt: rename fscrypt_master_key to fscrypt_direct_key Eric Biggers
2019-08-12 22:20   ` Theodore Y. Ts'o
2019-08-05 16:25 ` [PATCH v8 06/20] fscrypt: refactor key setup code in preparation for v2 policies Eric Biggers
2019-08-12 22:38   ` Theodore Y. Ts'o
2019-08-05 16:25 ` [PATCH v8 07/20] fscrypt: move v1 policy key setup to keysetup_v1.c Eric Biggers
2019-08-12 22:53   ` Theodore Y. Ts'o
2019-08-05 16:25 ` [PATCH v8 08/20] fscrypt: rename keyinfo.c to keysetup.c Eric Biggers
2019-08-12 22:53   ` Theodore Y. Ts'o
2019-08-05 16:25 ` [PATCH v8 09/20] fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl Eric Biggers
2019-08-05 16:25 ` [PATCH v8 10/20] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl Eric Biggers
2019-08-13  0:06   ` Theodore Y. Ts'o
2019-08-14 22:35     ` Eric Biggers [this message]
2019-08-05 16:25 ` [PATCH v8 11/20] fscrypt: add FS_IOC_GET_ENCRYPTION_KEY_STATUS ioctl Eric Biggers
2019-08-05 16:25 ` [PATCH v8 12/20] fscrypt: add an HKDF-SHA512 implementation Eric Biggers
2019-08-06 20:43   ` Paul Crowley
2019-08-05 16:25 ` [PATCH v8 13/20] fscrypt: v2 encryption policy support Eric Biggers
2019-08-06 20:44   ` Paul Crowley
2019-08-13  0:39   ` Theodore Y. Ts'o
2019-08-05 16:25 ` [PATCH v8 14/20] fscrypt: allow unprivileged users to add/remove keys for v2 policies Eric Biggers
2019-08-13  0:14   ` Theodore Y. Ts'o
2019-08-05 16:25 ` [PATCH v8 15/20] fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS ioctl Eric Biggers
2019-08-13  0:15   ` Theodore Y. Ts'o
2019-08-05 16:25 ` [PATCH v8 16/20] fscrypt: require that key be added when setting a v2 encryption policy Eric Biggers
2019-08-05 16:25 ` [PATCH v8 17/20] ext4: wire up new fscrypt ioctls Eric Biggers
2019-08-05 16:25 ` [PATCH v8 18/20] f2fs: " Eric Biggers
2019-08-05 16:25 ` [PATCH v8 19/20] ubifs: " Eric Biggers
2019-08-05 16:25 ` [PATCH v8 20/20] fscrypt: document the new ioctls and policy version Eric Biggers
2019-08-13  0:49   ` Theodore Y. Ts'o
2019-08-14 22:37 ` [PATCH v8 00/20] fscrypt: key management improvements Eric Biggers

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