On Thu, Sep 26, 2013 at 02:48:49AM +1000, Ben Skeggs wrote: > On Thu, Sep 26, 2013 at 12:41 AM, Pasi Kärkkäinen <pasik@xxxxxx> wrote: > > Hello, > > > > On Wed, Sep 04, 2013 at 08:59:13AM +0200, Maarten Lankhorst wrote: > >> Op 04-09-13 05:41, Ben Skeggs schreef: > >> > On Thu, Aug 22, 2013 at 5:12 PM, Maarten Lankhorst > >> > <maarten.lankhorst@xxxxxxxxxxxxx> wrote: > >> >> Op 22-08-13 02:10, Ilia Mirkin schreef: > >> >>> The code expects non-VRAM mem nodes to have a pages list. If that's not > >> >>> set, it will do a null deref down the line. Warn on that condition and > >> >>> return an error. > >> >>> > >> >>> See https://bugs.freedesktop.org/show_bug.cgi?id=64774 > >> >>> > >> >>> Reported-by: Pasi Kärkkäinen <pasik@xxxxxx> > >> >>> Tested-by: Pasi Kärkkäinen <pasik@xxxxxx> > >> >>> Signed-off-by: Ilia Mirkin <imirkin@xxxxxxxxxxxx> > >> >>> Cc: <stable@xxxxxxxxxxxxxxx> # 3.8+ > >> >>> --- > >> >>> > >> >>> I don't exactly understand what's going on, but this is just a > >> >>> straightforward way to avoid a null deref that you see happens in the > >> >>> bug. I haven't figured out the root cause of this, but it's getting > >> >>> well into the "I have no idea how TTM works" space. However this seems > >> >>> like a bit of defensive programming -- nouveau_vm_map_sg will pass > >> >>> node->pages as a list down, which will be dereferenced by > >> >>> nvc0_vm_map_sg. Perhaps the other arguments should make that > >> >>> dereferencing not happen, but it definitely was happening here, as you > >> >>> can see in the bug. > >> >>> > >> >>> Ben/Maarten, I'll let you judge whether this check is appropriate, > >> >>> since like I hope I was able to convey above, I'm just not really sure :) > >> >> Not it really isn't appropriate.. > >> >> > >> >> You'd have to call call nouveau_vm_map_sg_table instead, the only place that doesn't handle that correctly > >> >> is where it's not expected to be called. > >> >> > >> >> Here, have a completely untested patch to fix things... > >> >> > >> >> diff --git a/drivers/gpu/drm/nouveau/nouveau_display.c b/drivers/gpu/drm/nouveau/nouveau_display.c > >> >> --- a/drivers/gpu/drm/nouveau/nouveau_display.c > >> >> +++ b/drivers/gpu/drm/nouveau/nouveau_display.c > >> >> @@ -138,17 +143,26 @@ nouveau_user_framebuffer_create(struct drm_device *dev, > >> >> { > >> >> struct nouveau_framebuffer *nouveau_fb; > >> >> struct drm_gem_object *gem; > >> >> + struct nouveau_bo *nvbo; > >> >> int ret = -ENOMEM; > >> >> > >> >> gem = drm_gem_object_lookup(dev, file_priv, mode_cmd->handles[0]); > >> >> if (!gem) > >> >> return ERR_PTR(-ENOENT); > >> >> > >> >> + nvbo = nouveau_gem_object(gem); > >> >> + if (!(nvbo->valid_domains & NOUVEAU_GEM_DOMAIN_VRAM)) { > >> >> + nv_warn(nouveau_drm(dev), "Trying to create a fb in vram with" > >> >> + " valid_domains=%08x\n", nvbo->valid_domains); > >> >> + ret = -EINVAL; > >> >> + goto err_unref; > >> >> + } > >> >> + > >> > Definitely the right idea, we can't handle this case right now. > >> > However, we may someday want/need to be able to scan out of system > >> > memory, so this is the wrong place. > >> > > >> > I suspect the correct thing to do (which'll also handle the > >> > "defensive" part) is to bail in nouveau_bo_move() on attempts to move > >> > a DMA-BUF backed object into VRAM. > >> > > >> > Sound OK? > >> > > >> If it has a WARN_ON or something that would be ok, I didn't find any other places that attempt to move buffers to VRAM though, so it's probably harmless. > >> > > > > Ben/Maarten: Are you guys planning to take a look at this and submit another patch, or.. ? > > > > I tested the two earlier patches from this thread, and they both fixed the problem (hard kernel crash). > > I'm hoping this bug could be finally solved in the kernel.. > I shall be looking at it properly once I'm back from XDC next week. > Great, thanks! -- Pasi > Thanks, > Ben. > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
