Re: Announce: cryptoapi-2.4.3 [aka international crypto (non-)patch]

Herbert Valerio Riedel
2001-04-25T14:06:00Z

hi,

On Tue, 24 Apr 2001, Jari Ruusu wrote:
> linux-2.4.3-cryptoapi-hvr4/drivers/block/loop.c lines 270...279 after your
> kernel patch:
>
> static int lo_read_actor(read_descriptor_t * desc, struct page *page, unsigned long offset, unsigned long size)
> {
> char *kaddr;
> unsigned long count = desc->count;
> struct lo_read_data *p = (struct lo_read_data*)desc->buf;
> struct loop_device *lo = p->lo;
> unsigned long IV = loop_get_iv(lo, (page->index * PAGE_CACHE_SIZE + offset - lo->lo_offset) >> LO_IV_SECTOR_BITS);
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> if (size > count)
> size = count;
>
> Have you tested that code with partitions or files that are larger than
> 4 gigs? On systems where int is 32 bits, that computation overflows.
you're right, I actually had it right in the first place, but stupidly
rewrote it to overflow C:-)

it should have been more or less:

unsigned long IV = loop_get_iv(lo,
page->index * (PAGE_CACHE_SIZE >> LO_IV_SECTOR_BITS)
+ (offset - lo->lo_offset) >> LO_IV_SECTOR_BITS));

I'll be fixed in cryptoapi-2.4.3-hvr6 (see http://www.hvrlab.org/crypto/)

oh, and btw, it should only concern file backed loop's... block devices,
as partitions, should have worked fine...

> If you want 512 byte based IV computation without modifying your kernel at
> all, you can use the loop.o module from my loop-AES package. I haven't tried
> using your modules based cryptoapi and my loop-AES drivers together, but I
> don't see any obvious reason why they couldn't be used simultaneously.

erm... I've looked at your patch... you do just the same thing as I do, as
it concerns 'changing the kernel'... but you do it in a 'static' way... I
want it to be changeable at runtime... and letting the way open to add
more IV calculation variants in the future, which every filter can choose
among at initialization...

> Linux-crypto: cryptography in and on the Linux system
> Archive: http://mail.nl.linux.org/linux-crypto/