Messages in this thread | | | Date | Mon, 21 Jul 2003 17:26:46 +0200 | From | Petr Vandrovec <> | Subject | How is info->cmap supposed to work? |
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Hi James, I have few problems with understanding how info->cmap is supposed to work:
(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.
(2) FBIOPUTCMAP calls fb_set_cmap, which in turn calls fb_setcolreg. FBIOGETCMAP copies cmap entries from info->cmap (after fixing (1)). Does it mean that fb_setcolreg has to fill 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.
(3) And who is supposed to initialize info->cmap, and to what value? It looks to me like that fbdev driver is supposed to do:
memset(&info->cmap, 0, sizeof(info->cmap)); fb_alloc_cmap(&info->cmap, 256, 1);
Is it right? What about fb_init_cmap() then? And why fbdev has to play with info->cmap, cannot generic layer take a care of this, if all info->cmap accesses go through generic layer, and fbdev driver itself has no need for this field?
Thanks, Petr Vandrovec vandrove@vc.cvut.cz
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