Re: [RFC PATCH] efivarfs: define integrity_read method
From: Al Viro <viro@ZenIV.linux.org.uk>
Date: 2017-07-06 12:46:03
Also in:
linux-fsdevel, linux-security-module
On Thu, Jul 06, 2017 at 08:14:01AM -0400, Mimi Zohar wrote:
This patch defines an ->integrity_read file operation method to read data for integrity hash collection.
quoted hunk ↗ jump to hunk
-static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf, - size_t count, loff_t *ppos) +static ssize_t __efivarfs_file_read(struct file *file, char __user *userbuf, + size_t count, loff_t *ppos, + struct iov_iter *iter) { struct efivar_entry *var = file->private_data; unsigned long datasize = 0;@@ -96,14 +98,32 @@ static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf, goto out_free; memcpy(data, &attributes, sizeof(attributes)); - size = simple_read_from_buffer(userbuf, count, ppos, - data, datasize + sizeof(attributes)); + + if (!iter) + size = simple_read_from_buffer(userbuf, count, ppos, data, + datasize + sizeof(attributes)); + else + size = copy_to_iter(data, datasize + sizeof(attributes), iter);
Egads... This kind of kludges is too ugly to exist. What the hell for? If you
want to define something that looks like ->read_iter(), bloody make it proper
read_iter. Really working one, that is - without this "our oh-so-special needs
do not include file position" crap.
Seriously, this kind of calling conventions alone is enough for a NAK with
extreme prejudice. Something like
ssize_t simple_read_iter_from_buffer(struct kiocb *iocb, struct iov_iter *to,
const void *from, size_t available)
{
loff_t pos = iocb->ki_pos;
size_t ret;
if (pos < 0)
return -EINVAL;
if (pos >= available)
return 0;
ret = copy_to_iter(to, from + pos, available - pos);
if (!ret && iov_iter_count(to))
return -EFAULT;
iocb->ki_pos = pos + ret;
return ret;
}
EXPORT_SYMBOL(simple_read_iter_from_buffer);
in fs/libfs.c and turn the efivarfs_file_read() into a real ->read_iter() by
replacing simple_read_from_buffer to simple_read_iter_from_buffer (and adjusting
the arguments, of course). All there is to it. Sheesh...