Re: [PATCH] uaccess: Disallow > INT_MAX copy sizes

Kees Cook
2019-09-23T23:08:59Z

On Sun, Aug 25, 2019 at 04:18:56PM -0700, Kees Cook wrote:
> As we've done with VFS, string operations, etc, reject usercopy sizes
> larger than INT_MAX, which would be nice to have for catching bugs
> related to size calculation overflows[1].
>
> This adds 10 bytes to x86_64 defconfig text and 1980 bytes to the data
> section:
>
> text data bss dec hex filename
> 19691167 5134320 1646664 26472151 193eed7 vmlinux.before
> 19691177 5136300 1646664 26474141 193f69d vmlinux.after
>
> [1] https://marc.info/?l=linux-s390&m=156631939010493&w=2
>
> Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>

ping! Andrew, can you take this?

-Kees

> ---
> include/linux/thread_info.h | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
> index 659a4400517b..e93e249a4e9b 100644
> --- a/include/linux/thread_info.h
> +++ b/include/linux/thread_info.h
> @@ -147,6 +147,8 @@ check_copy_size(const void *addr, size_t bytes, bool is_source)
> __bad_copy_to();
> return false;
> }
> + if (WARN_ON_ONCE(bytes > INT_MAX))
> + return false;
> check_object_size(addr, bytes, is_source);
> return true;
> }
> --
> 2.17.1
>
>
> --
> Kees Cook

--
Kees Cook