diff mbox series

quota: explicitly forbid quota files from being encrypted

Message ID 20230905003227.326998-1-ebiggers@kernel.org (mailing list archive)
State Accepted
Headers show
Series quota: explicitly forbid quota files from being encrypted | expand

Commit Message

Eric Biggers Sept. 5, 2023, 12:32 a.m. UTC
From: Eric Biggers <ebiggers@google.com>

Since commit d7e7b9af104c ("fscrypt: stop using keyrings subsystem for
fscrypt_master_key"), xfstest generic/270 causes a WARNING when run on
f2fs with test_dummy_encryption in the mount options:

$ kvm-xfstests -c f2fs/encrypt generic/270
[...]
WARNING: CPU: 1 PID: 2453 at fs/crypto/keyring.c:240 fscrypt_destroy_keyring+0x1f5/0x260

The cause of the WARNING is that not all encrypted inodes have been
evicted before fscrypt_destroy_keyring() is called, which violates an
assumption.  This happens because the test uses an external quota file,
which gets automatically encrypted due to test_dummy_encryption.

Encryption of quota files has never really been supported.  On ext4,
ext4_quota_read() does not decrypt the data, so encrypted quota files
are always considered invalid on ext4.  On f2fs, f2fs_quota_read() uses
the pagecache, so trying to use an encrypted quota file gets farther,
resulting in the issue described above being possible.  But this was
never intended to be possible, and there is no use case for it.

Therefore, make the quota support layer explicitly reject using
IS_ENCRYPTED inodes when quotaon is attempted.

Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/quota/dquot.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)


base-commit: 708283abf896dd4853e673cc8cba70acaf9bf4ea

Comments

Jan Kara Sept. 5, 2023, 9:11 a.m. UTC | #1
On Mon 04-09-23 17:32:27, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Since commit d7e7b9af104c ("fscrypt: stop using keyrings subsystem for
> fscrypt_master_key"), xfstest generic/270 causes a WARNING when run on
> f2fs with test_dummy_encryption in the mount options:
> 
> $ kvm-xfstests -c f2fs/encrypt generic/270
> [...]
> WARNING: CPU: 1 PID: 2453 at fs/crypto/keyring.c:240 fscrypt_destroy_keyring+0x1f5/0x260
> 
> The cause of the WARNING is that not all encrypted inodes have been
> evicted before fscrypt_destroy_keyring() is called, which violates an
> assumption.  This happens because the test uses an external quota file,
> which gets automatically encrypted due to test_dummy_encryption.
> 
> Encryption of quota files has never really been supported.  On ext4,
> ext4_quota_read() does not decrypt the data, so encrypted quota files
> are always considered invalid on ext4.  On f2fs, f2fs_quota_read() uses
> the pagecache, so trying to use an encrypted quota file gets farther,
> resulting in the issue described above being possible.  But this was
> never intended to be possible, and there is no use case for it.
> 
> Therefore, make the quota support layer explicitly reject using
> IS_ENCRYPTED inodes when quotaon is attempted.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Looks good. I'll queue this patch into my tree and send it to Linus for
RC2.

								Honza

> ---
>  fs/quota/dquot.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
> index 9e72bfe8bbad9..7e268cd2727cc 100644
> --- a/fs/quota/dquot.c
> +++ b/fs/quota/dquot.c
> @@ -2339,6 +2339,20 @@ static int vfs_setup_quota_inode(struct inode *inode, int type)
>  	if (sb_has_quota_loaded(sb, type))
>  		return -EBUSY;
>  
> +	/*
> +	 * Quota files should never be encrypted.  They should be thought of as
> +	 * filesystem metadata, not user data.  New-style internal quota files
> +	 * cannot be encrypted by users anyway, but old-style external quota
> +	 * files could potentially be incorrectly created in an encrypted
> +	 * directory, hence this explicit check.  Some reasons why encrypted
> +	 * quota files don't work include: (1) some filesystems that support
> +	 * encryption don't handle it in their quota_read and quota_write, and
> +	 * (2) cleaning up encrypted quota files at unmount would need special
> +	 * consideration, as quota files are cleaned up later than user files.
> +	 */
> +	if (IS_ENCRYPTED(inode))
> +		return -EINVAL;
> +
>  	dqopt->files[type] = igrab(inode);
>  	if (!dqopt->files[type])
>  		return -EIO;
> 
> base-commit: 708283abf896dd4853e673cc8cba70acaf9bf4ea
> -- 
> 2.42.0
>
diff mbox series

Patch

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 9e72bfe8bbad9..7e268cd2727cc 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -2339,6 +2339,20 @@  static int vfs_setup_quota_inode(struct inode *inode, int type)
 	if (sb_has_quota_loaded(sb, type))
 		return -EBUSY;
 
+	/*
+	 * Quota files should never be encrypted.  They should be thought of as
+	 * filesystem metadata, not user data.  New-style internal quota files
+	 * cannot be encrypted by users anyway, but old-style external quota
+	 * files could potentially be incorrectly created in an encrypted
+	 * directory, hence this explicit check.  Some reasons why encrypted
+	 * quota files don't work include: (1) some filesystems that support
+	 * encryption don't handle it in their quota_read and quota_write, and
+	 * (2) cleaning up encrypted quota files at unmount would need special
+	 * consideration, as quota files are cleaned up later than user files.
+	 */
+	if (IS_ENCRYPTED(inode))
+		return -EINVAL;
+
 	dqopt->files[type] = igrab(inode);
 	if (!dqopt->files[type])
 		return -EIO;