Hi Mimi,
On 2020-05-18 5:37 a.m., Mimi Zohar wrote:
Hi Christoph,
On Sun, 2020-05-17 at 23:22 -0700, Christoph Hellwig wrote:
On Fri, May 15, 2020 at 09:29:33PM +0000, Luis Chamberlain wrote:
On Wed, May 13, 2020 at 11:17:36AM -0700, Christoph Hellwig wrote:
Can you also move kernel_read_* out of fs.h? That header gets pulled
in just about everywhere and doesn't really need function not related
to the general fs interface.
Sure, where should I dump these?
Maybe a new linux/kernel_read_file.h? Bonus points for a small top
of the file comment explaining the point of the interface, which I
still don't get :)
Instead of rolling your own method of having the kernel read a file,
which requires call specific security hooks, this interface provides a
single generic set of pre and post security hooks. The
kernel_read_file_id enumeration permits the security hook to
differentiate between callers.
To comply with secure and trusted boot concepts, a file cannot be
accessible to the caller until after it has been measured and/or the
integrity (hash/signature) appraised.
In some cases, the file was previously read twice, first to measure
and/or appraise the file and then read again into a buffer for
use. This interface reads the file into a buffer once, calls the
generic post security hook, before providing the buffer to the caller.
(Note using firmware pre-allocated memory might be an issue.)
Partial reading firmware will result in needing to pre-read the entire
file, most likely on the security pre hook.
The entire file may be very large and not fit into a buffer.
Hence one of the reasons for a partial read of the file.
For security purposes, you need to change your code to limit the amount
of data it reads into a buffer at one time to not consume or run out of
much memory.
Mimi
Scott
