On Mon, Oct 2, 2023 at 12:04 AM Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
>
> The buffer->pages[] has "buffer->pagecount" elements so this > comparison
> has to be changed to >= to avoid reading beyond the end of the array.
> The buffer->pages[] array is allocated in cma_heap_allocate().
>
> Fixes: a5d2d29e24be ("dma-buf: heaps: Move heap-helper logic into the cma_heap implementation")
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> ---
> drivers/dma-buf/heaps/cma_heap.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
> index ee899f8e6721..bea7e574f916 100644
> --- a/drivers/dma-buf/heaps/cma_heap.c
> +++ b/drivers/dma-buf/heaps/cma_heap.c
> @@ -165,7 +165,7 @@ static vm_fault_t cma_heap_vm_fault(struct vm_fault *vmf)
> struct vm_area_struct *vma = vmf->vma;
> struct cma_heap_buffer *buffer = vma->vm_private_data;
>
> - if (vmf->pgoff > buffer->pagecount)
> + if (vmf->pgoff >= buffer->pagecount)
> return VM_FAULT_SIGBUS;
>
Hi Dan,
Your fix looks correct to me, but I'm curious if you observed this
problem on a device? The mmap in dma-buf.c looks like it prevents
creating a mapping that is too large, and I think an access beyond the
VMA should segfault before reaching here.
Thanks,
T.J.
