From 1bb1d4252d1ede47afea054979fb9d95fc891743 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Thu, 8 Sep 2016 14:20:38 -0700 Subject: [PATCH] fscrypto: require write access to mount to set encryption policy 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 Signed-off-by: Theodore Ts'o Acked-by: Jaegeuk Kim Signed-off-by: Greg Kroah-Hartman --- fs/f2fs/file.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 4b449d263333..01eed94b01ea 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -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;