On Fri, Jan 27, 2023 at 01:10:46PM +0100, Takashi Iwai wrote: > On Tue, 03 Jan 2023 15:07:55 +0100, > Takashi Iwai wrote: > > > > On Fri, 30 Dec 2022 08:27:58 +0100, > > Zheng Wang wrote: > > > > > > Here is a function call chain. > > > nvkm_vmm_pfn_map->nvkm_vmm_pfn_split_merge->nvkm_vmm_node_split > > > If nvkm_vma_tail return NULL in nvkm_vmm_node_split, it will > > > finally invoke nvkm_vmm_node_merge->nvkm_vmm_node_delete, which > > > will free the vma. However, nvkm_vmm_pfn_map didn't notice that. > > > It goes into next label and UAF happens. > > > > > > Fix it by returning the return-value of nvkm_vmm_node_merge > > > instead of NULL. > > > > > > Signed-off-by: Zheng Wang <zyytlz.wz@xxxxxxx> > > > > FWIW, CVE-2023-0030 has been assigned to this bug. > > It's a question whether it really deserves as a security issue, but a > > bug is a bug... > > > > Ben, could you review this please? > > A gentle ping as reminder. The bug is still present. This was also reported in [1]. I had a closer look and FWICT this code is fine and there isn't a bug. Zheng Wang, the reporter of the BZ, also confirmed this to be a false positive from CodeQL. Anyway, here's the explaination I also posted in the BZ: "In nvkm_vmm_node_merge() nvkm_vmm_node_delete() is only called when prev is set. However, prev is NULL unless we enter the "if (vma->addr != addr)" path in nvkm_vmm_node_split(). In such a case the vma pointer, which is also passed to nvkm_vmm_node_merge(), is set to a freshly allocated struct nvkm_vma with nvkm_vma_tail() right before prev is set to the old vma pointer. Hence, the only thing happening there when nvkm_vma_tail() fails in the "if (vma->size != size)" path is that either nvkm_vmm_node_merge() does nothing in case prev wasn't set or it merges and frees the new vma created in the "if (vma->addr != addr)" path. Or in other words the proper cleanup for the error condition is done. I can't see any case where the original vma pointer given by nvkm_vmm_pfn_map() is actually freed." [1] https://bugzilla.redhat.com/show_bug.cgi?id=2157041 - Danilo > > > thanks, > > Takashi > > > > > > > thanks, > > > > Takashi > > > > > --- > > > drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c | 4 ++-- > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c b/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c > > > index ae793f400ba1..84d6fc87b2e8 100644 > > > --- a/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c > > > +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c > > > @@ -937,8 +937,8 @@ nvkm_vmm_node_split(struct nvkm_vmm *vmm, > > > if (vma->size != size) { > > > struct nvkm_vma *tmp; > > > if (!(tmp = nvkm_vma_tail(vma, vma->size - size))) { > > > - nvkm_vmm_node_merge(vmm, prev, vma, NULL, vma->size); > > > - return NULL; > > > + tmp = nvkm_vmm_node_merge(vmm, prev, vma, NULL, vma->size); > > > + return tmp; > > > } > > > tmp->part = true; > > > nvkm_vmm_node_insert(vmm, tmp); > > > -- > > > 2.25.1 > > > >
