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fscrypto: require write access to mount to set encryption policy

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commit ba63f23d69a3a10e7e527a02702023da68ef8a6d upstream.

[Please apply to 4.4-stable.  Note: this was already backported, but
only to ext4; it was missed that it should go to f2fs as well.  This is
needed to make xfstest generic/395 pass on f2fs.]

Since setting an encryption policy requires writing metadata to the
filesystem, it should be guarded by mnt_want_write/mnt_drop_write.
Otherwise, a user could cause a write to a frozen or readonly
filesystem.  This was handled correctly by f2fs but not by ext4.  Make
fscrypt_process_policy() handle it rather than relying on the filesystem
to get it right.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric Biggers 2016-09-08 14:20:38 -07:00 committed by Greg Kroah-Hartman
parent 8a004caec1
commit 1bb1d4252d
1 changed files with 6 additions and 0 deletions
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6
fs/f2fs/file.c
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@ -1541,12 +1541,18 @@ static int f2fs_ioc_set_encryption_policy(struct file *filp, unsigned long arg)
sizeof(policy)))
return -EFAULT;
err = mnt_want_write_file(filp);
if (err)
return err;
mutex_lock(&inode->i_mutex);
err = f2fs_process_policy(&policy, inode);
mutex_unlock(&inode->i_mutex);
mnt_drop_write_file(filp);
return err;
#else
return -EOPNOTSUPP;