Messages in this thread | | | Date | Fri, 14 Apr 2023 09:28:54 +0200 | Subject | Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access | From | Thomas Zimmermann <> |
| |
Hi
Am 13.04.23 um 22:01 schrieb Daniel Vetter: > On Thu, Apr 13, 2023 at 09:20:23PM +0200, Thomas Zimmermann wrote: >> Hi >> >> Am 13.04.23 um 20:56 schrieb Daniel Vetter: >> [...] >>> >>> This should switch the existing code over to using drm_framebuffer instead >>> of fbdev: >>> >>> >>> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c >>> index ef4eb8b12766..99ca69dd432f 100644 >>> --- a/drivers/gpu/drm/drm_fb_helper.c >>> +++ b/drivers/gpu/drm/drm_fb_helper.c >>> @@ -647,22 +647,26 @@ static void drm_fb_helper_damage(struct drm_fb_helper *helper, u32 x, u32 y, >>> static void drm_fb_helper_memory_range_to_clip(struct fb_info *info, off_t off, size_t len, >>> struct drm_rect *clip) >>> { >>> + struct drm_fb_helper *helper = info->par; >>> + >>> off_t end = off + len; >>> u32 x1 = 0; >>> u32 y1 = off / info->fix.line_length; >>> - u32 x2 = info->var.xres; >>> - u32 y2 = DIV_ROUND_UP(end, info->fix.line_length); >>> + u32 x2 = helper->fb->height; >>> + unsigned stride = helper->fb->pitches[0]; >>> + u32 y2 = DIV_ROUND_UP(end, stride); >>> + int bpp = drm_format_info_bpp(helper->fb->format, 0); >> >> Please DONT do that. The code here is fbdev code and shouldn't bother about >> DRM data structures. Actually, it shouldn't be here: a number of fbdev >> drivers with deferred I/O contain similar code and the fbdev module should >> provide us with a helper. (I think I even had some patches somewhere.) > > Well my thinking is that it's a drm driver, so if we have issue with limit
Technically, it's not a driver, but a client.
> checks blowing up it makes more sense to check them against drm limits.
You can still do this in fb_dirty during the actual update.
> Plus a lot more people understand those than fbdev. They should all match > anyway, or if they dont, we have a bug. The thing is, if you change this > further to just pass the drm_framebuffer, then this 100% becomes a drm > function, which could be used by anything in drm really.
The code is only useful to fbdev-generic and a number older of fbdev drivers. Nothing else uses deferred I/O and the rsp damage handling. Anything else operates directly on memory buffers. (i915 is a bit special, but doesn't use this damage handling.) The function really should not be here.
I'd push back on additional DRM code with fbdev deferred I/O. Drivers' fbdev should either operate directly on GEM buffers; or the driver should employ fbdev-generic.
Best regards Thomas
> > But also *shrug*. > -Daniel
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev [unhandled content-type:application/pgp-signature] | |