Quoting Ben Skeggs <bskeggs@xxxxxxxxxx>:
On Wed, Feb 14, 2018 at 1:40 AM, Gustavo A. R. Silva <garsilva@xxxxxxxxxxxxxx> wrote:Hi all, While doing some static analysis I ran into the following piece of code at drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c:957: 957#define node(root, dir) ((root)->head.dir == &vmm->list) ? NULL : \ 958 list_entry((root)->head.dir, struct nvkm_vma, head) 959 960void 961nvkm_vmm_unmap_region(struct nvkm_vmm *vmm, struct nvkm_vma *vma) 962{ 963 struct nvkm_vma *next; 964 965 nvkm_memory_tags_put(vma->memory, vmm->mmu->subdev.device, &vma->tags); 966 nvkm_memory_unref(&vma->memory); 967 968 if (vma->part) { 969 struct nvkm_vma *prev = node(vma, prev); 970 if (!prev->memory) { 971 prev->size += vma->size; 972 rb_erase(&vma->tree, &vmm->root); 973 list_del(&vma->head); 974 kfree(vma); 975 vma = prev; 976 } 977 } 978 979 next = node(vma, next); 980 if (next && next->part) { 981 if (!next->memory) { 982 vma->size += next->size; 983 rb_erase(&next->tree, &vmm->root); 984 list_del(&next->head); 985 kfree(next); 986 } 987 } 988} The issue here is that in case _node_ returns NULL, _prev_ is not being null checked, hence there is a potential null pointer dereference at line 970. Notice that _next_ is being null checked at line 980, so I wonder if _prev_ should be checked the same as _next_. The fact that both _next_ and next->part are null checked, makes me wonder if in case _prev_ actually needs to be checked, there is another pointer contained into _prev_ to be validated as well? I'm sorry, this is not clear to me at this moment.It's not checked because it can't happen. If vma->part is set, there will be a previous node that it was split from.
I got it. Thanks, Ben. -- Gustavo _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
