On Tue, Sep 21, 2021 at 3:22 PM Tim Gardner tim.gardner@canonical.com wrote:

On 9/20/21 8:07 PM, Karol Herbst wrote:

...

On Mon, Sep 20, 2021 at 8:17 PM Tim Gardner tim.gardner@canonical.com wrote:

...

Coverity complains of a resource leak in ga102_chan_new():

CID 119637 (#7 of 7): Resource leak (RESOURCE_LEAK) 13. leaked_storage: Variable chan going out of scope leaks the storage it points to. 190 return ret;

Fix this by freeing 'chan' in the error path.

yeah, this is actually a false positive. I ran your patch through kasan and got a use-after-free as we deallocate the passed in pointer after calling the function pointer to the new function. One might argue that the programming style isn't the best and we should be explicit about freeing memory though.

So the caller of this constructor has to look at the error return code and decide whether the value stored in *pobject can be freed ? I guess if the caller initializes the value at *pobject to be NULL then it can kfree() regardless.

yeah, so *pobject is set, hence the caller freeing the object on error. I am not a big fan of this to be honest, but Ben told me he has a bigger rework of how all of this works pending anyway and I think we should keep things like this in mind so it's easier for others to understand if the code is actually correct or not.

Anyway, this all happens inside nvkm_ioctl_new. We have the call to "oclass.ctor(&oclass, data, size, &object)" which ends up calling ga102_chan_new, and on error we do "nvkm_object_del(&object)", which does some cleanups and calls kfree.

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Cc: Ben Skeggs bskeggs@redhat.com Cc: David Airlie airlied@linux.ie Cc: Daniel Vetter daniel@ffwll.ch Cc: Karol Herbst kherbst@redhat.com Cc: dri-devel@lists.freedesktop.org Cc: nouveau@lists.freedesktop.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Tim Gardner tim.gardner@canonical.com

---

.../gpu/drm/nouveau/nvkm/engine/fifo/ga102.c | 20 ++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/fifo/ga102.c b/drivers/gpu/drm/nouveau/nvkm/engine/fifo/ga102.c index f897bef13acf..4dbdfb53e65f 100644 --- a/drivers/gpu/drm/nouveau/nvkm/engine/fifo/ga102.c +++ b/drivers/gpu/drm/nouveau/nvkm/engine/fifo/ga102.c @@ -175,19 +175,21 @@ ga102_chan_new(struct nvkm_device *device, } }

•   if (!chan->ctrl.runl)
  

•           return -ENODEV;
  

•   if (!chan->ctrl.runl) {
  

•           ret = -ENODEV;
  

•           goto free_chan;
  

•   }
  
     chan->ctrl.chan = nvkm_rd32(device, chan->ctrl.runl + 0x004) & 0xfffffff0;
     args->token = nvkm_rd32(device, chan->ctrl.runl + 0x008) & 0xffff0000;
  
     ret = nvkm_memory_new(device, NVKM_MEM_TARGET_INST, 0x1000, 0x1000, true, &chan->mthd);
     if (ret)
  

•           return ret;
  

•           goto free_chan;
  
     ret = nvkm_memory_new(device, NVKM_MEM_TARGET_INST, 0x1000, 0x1000, true, &chan->inst);
     if (ret)
  

•           return ret;
  

•           goto free_chan;
  
     nvkm_kmap(chan->inst);
     nvkm_wo32(chan->inst, 0x010, 0x0000face);
  

@@ -209,11 +211,11 @@ ga102_chan_new(struct nvkm_device *device,

     ret = nvkm_memory_new(device, NVKM_MEM_TARGET_INST, 0x1000, 0x1000, true, &chan->user);
     if (ret)

•           return ret;
  

•           goto free_chan;
  
     ret = nvkm_memory_new(device, NVKM_MEM_TARGET_INST, 0x1000, 0x1000, true, &chan->runl);
     if (ret)
  

•           return ret;
  

•           goto free_chan;
  
     nvkm_kmap(chan->runl);
     nvkm_wo32(chan->runl, 0x00, 0x80030001);
  

@@ -228,10 +230,14 @@ ga102_chan_new(struct nvkm_device *device,

     ret = nvkm_vmm_join(vmm, chan->inst);
     if (ret)

•           return ret;
  

•           goto free_chan;
  
     chan->vmm = nvkm_vmm_ref(vmm);
     return 0;
  

+free_chan:

•   kfree(chan);
  

•   return ret;
  

  }

  static const struct nvkm_device_oclass

-- 2.33.0

--

Tim Gardner Canonical, Inc