On Tue, Jun 19, 2018 at 05:57:35PM -0700, Alistair Strachan wrote:
> The ashmem driver did not check that the size/offset of the vma passed
> to its .mmap() function was not larger than the ashmem object being
> mapped. This could cause mmap() to succeed, even though accessing parts
> of the mapping would later fail with a segmentation fault.
>
> Ensure an error is returned by the ashmem_mmap() function if the vma
> size is larger than the ashmem object size. This enables safer handling
> of the problem in userspace.
>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Arve Hjønnevåg <arve@xxxxxxxxxxx>
> Cc: Todd Kjos <tkjos@xxxxxxxxxxx>
> Cc: Martijn Coenen <maco@xxxxxxxxxxx>
> Cc: devel@xxxxxxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: kernel-team@xxxxxxxxxxx
> Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Alistair Strachan <astrachan@xxxxxxxxxx>
> ---
> v2: Removed unnecessary use of unlikely() macro
>
> drivers/staging/android/ashmem.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c
> index c6386e4f5c9b..e392358ec244 100644
> --- a/drivers/staging/android/ashmem.c
> +++ b/drivers/staging/android/ashmem.c
> @@ -366,6 +366,12 @@ static int ashmem_mmap(struct file *file, struct vm_area_struct *vma)
> goto out;
> }
>
> + /* requested mapping size larger than object size */
> + if (vma->vm_end - vma->vm_start > PAGE_ALIGN(asma->size)) {
> + ret = -EINVAL;
> + goto out;
> + }
> +
Acked-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
thanks,
- Joel
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