From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maarten Lankhorst Subject: Re: [PATCH] drm/nouveau: avoid null deref on bad arguments to nouveau_vma_getmap Date: Wed, 04 Sep 2013 08:59:13 +0200 Message-ID: <5226DA41.5060203@canonical.com> References: <1377130214-17522-1-git-send-email-imirkin@alum.mit.edu> <5215B9E8.5080108@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: nouveau-bounces+gcfxn-nouveau=m.gmane.org-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org Errors-To: nouveau-bounces+gcfxn-nouveau=m.gmane.org-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org To: Ben Skeggs Cc: "nouveau-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org" , "dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org" , Ben Skeggs List-Id: nouveau.vger.kernel.org Op 04-09-13 05:41, Ben Skeggs schreef: > On Thu, Aug 22, 2013 at 5:12 PM, Maarten Lankhorst > 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=3D64774 >>> >>> Reported-by: Pasi K=E4rkk=E4inen >>> Tested-by: Pasi K=E4rkk=E4inen >>> Signed-off-by: Ilia Mirkin >>> Cc: # 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 =3D -ENOMEM; >> >> gem =3D drm_gem_object_lookup(dev, file_priv, mode_cmd->handles[= 0]); >> if (!gem) >> return ERR_PTR(-ENOENT); >> >> + nvbo =3D 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=3D%08x\n", nvbo->valid_domains); >> + ret =3D -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 harmle= ss. When looking into this bug I noticed that nouveau_bo_vma_add needs to have = a check for nvbo->page_shift =3D=3D vma->vm->vmm->spg_shift, and only if the check is true it should map the page in TTM_PL_TT. Patch be= low. Should probably also be cc'd to stable. ~Maarten diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau= /nouveau_bo.c index 89b992e..355a1b7 100644 --- a/drivers/gpu/drm/nouveau/nouveau_bo.c +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c @@ -1560,7 +1560,8 @@ nouveau_bo_vma_add(struct nouveau_bo *nvbo, struct no= uveau_vm *vm, = if (nvbo->bo.mem.mem_type =3D=3D TTM_PL_VRAM) nouveau_vm_map(vma, nvbo->bo.mem.mm_node); - else if (nvbo->bo.mem.mem_type =3D=3D TTM_PL_TT) { + else if (nvbo->bo.mem.mem_type =3D=3D TTM_PL_TT && + nvbo->page_shift =3D=3D vma->vm->vmm->spg_shift) { if (node->sg) nouveau_vm_map_sg_table(vma, 0, size, node); else