On 25 Jul 03 at 1:04, James Simmons wrote:
>
> Hi!
Finally ;-) I just posted on lk that nobody answered...
> > (1) FBIOGETCMAP calls fb_copy_cmap(&info->cmap, &cmap, 0);
> > Should not it use last argument of '2', as &cmap points
> > to the userspace? It looks to me like that anybody can
> > overwrite kernel currently... Only positive side is that
> > there is no way to control info->cmap contents (see (2)),
> > so you can only crash kernel with random code, you cannot
> > stuff some malicious code there.
>
> I think I posted something about that some time ago and I didn't here
> anything. Looking at the code I realized that yeap its broke. Its strange
> that both fb_set_cmap and fb_copy_cmap can get data from userland. I would
> think that we either have fb_set_cmap just set the video hardware or
> have fb_set_cmap be able to grab data from userland and fb_copy_cmap send
> data to userland.
It looks reasonable.
> > (2) FBIOPUTCMAP calls fb_set_cmap, which in turn calls
> > fb_setcolreg.
>
> True.
>
> > FBIOGETCMAP copies cmap entries from
> > info->cmap (after fixing (1)). Does it mean that
> > fb_setcolreg has to fill info->cmap itself?
>
> No. At present all the drivers initialize a default cmap. Then it
> doesn't matter which function gets called first.
Problem is that if you do FBIOPUTCMAP to change (say) entry #0,
FBIOGETCMAP will retrieve default value of entry #0 instead of value
you just set with FBIOPUTCMAP, unless driver updates its info->cmap
itself...
> > Is not it
> > a bit ugly? And fb_set_cmap documentation is incorrect:
> > kspc == 0 means copy from userspace, while
> > kspc != 0 means copy "local", inside kernel-space. Documentation
> > says that 0 is local, while 1 is get_user.
>
> :-( I have to look to see if that has been around for a while. I have a
> feeling it has been.
2.4.x does same. But I do not think that it is excuse ;-)
> The reason for the driver initalizing the default cmap is because
> we don't know how big the actual colormap will be. I don't know if
> the generic method of setting to color map to 2^bpp until above 8 bpp
> mode in which case we only set 16 colors will always work. Perhaps we
> could just set the cmap.len field and have the upper layer just generate
> from that.
Ok, then there is a problem - as nothing in matroxfb uses info->cmap,
I did not saw any need to initialize it. I'll fix it.
Petr
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This archive was generated by hypermail 2b29 : Thu Jul 31 2003 - 22:00:24 EST