linux-kernel - [PATCH 4.4 24/28] fscrypto: lock inode while setting encryption policy

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Date:   Mon, 20 Mar 2017 18:49:19 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Biggers <ebiggers@...gle.com>,
        Theodore Tso <tytso@....edu>,
        Richard Weinberger <richard@....at>
Subject: [PATCH 4.4 24/28] fscrypto: lock inode while setting encryption policy

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Biggers <ebiggers@...gle.com>

commit 8906a8223ad4909b391c5628f7991ebceda30e52 upstream.

i_rwsem needs to be acquired while setting an encryption policy so that
concurrent calls to FS_IOC_SET_ENCRYPTION_POLICY are correctly
serialized (especially the ->get_context() + ->set_context() pair), and
so that new files cannot be created in the directory during or after the
->empty_dir() check.

Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Reviewed-by: Richard Weinberger <richard@....at>
Cc: stable@...r.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>


---
 fs/ext4/ioctl.c |    4 ++++
 fs/f2fs/file.c  |    9 ++++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -633,8 +633,12 @@ resizefs_out:
 		if (err)
 			goto encryption_policy_out;
 
+		mutex_lock(&inode->i_mutex);
+
 		err = ext4_process_policy(&policy, inode);
 
+		mutex_unlock(&inode->i_mutex);
+
 		mnt_drop_write_file(filp);
 encryption_policy_out:
 		return err;
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1535,12 +1535,19 @@ static int f2fs_ioc_set_encryption_polic
 #ifdef CONFIG_F2FS_FS_ENCRYPTION
 	struct f2fs_encryption_policy policy;
 	struct inode *inode = file_inode(filp);
+	int err;
 
 	if (copy_from_user(&policy, (struct f2fs_encryption_policy __user *)arg,
 				sizeof(policy)))
 		return -EFAULT;
 
-	return f2fs_process_policy(&policy, inode);
+	mutex_lock(&inode->i_mutex);
+
+	err = f2fs_process_policy(&policy, inode);
+
+	mutex_unlock(&inode->i_mutex);
+
+	return err;
 #else
 	return -EOPNOTSUPP;
 #endif