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. Thanks, Ben. > > Thanks, > > -- Pasi > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
