fscrypto: require write access to mount to set encryption policy

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 <[email protected]>
Cc: [email protected] # 4.1+; check fs/{ext4,f2fs}
Signed-off-by: Theodore Ts'o <[email protected]>
Acked-by: Jaegeuk Kim <[email protected]>

0 files changed, 0 insertions, 0 deletions