On Mon, May 18, 2020 at 08:37:42AM -0400, 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. Well described! :) -- Kees Cook
