Re: [PATCH] ksys_mount: check for permissions before resource allocation

Ilya Matveychikov
2018-06-05T07:00:03Z

Just CC’ed to some of maintainers.

$ perl scripts/get_maintainer.pl fs/0001-ksys_mount-check-for-permissions-before-resource-all.patch
Alexander Viro <viro@zeniv.linux.org.uk> (maintainer:FILESYSTEMS (VFS and infrastructure))
linux-fsdevel@vger.kernel.org (open list:FILESYSTEMS (VFS and infrastructure))
linux-kernel@vger.kernel.org (open list)

> On Jun 5, 2018, at 6:00 AM, Ilya Matveychikov <matvejchikov@gmail.com> wrote:
>
> Early check for mount permissions prevents possible allocation of 3
> pages from kmalloc() pool by unpriveledged user which can be used for
> spraying the kernel heap.
>
> Signed-off-by: Ilya V. Matveychikov <matvejchikov@gmail.com>
> ---
> fs/namespace.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index 5f75969adff1..1ef8feb2de2a 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -3046,6 +3046,9 @@ int ksys_mount(char __user *dev_name, char __user *dir_name, char __user *type,
> char *kernel_dev;
> void *options;
>
> + if (!may_mount())
> + return -EPERM;
> +
> kernel_type = copy_mount_string(type);
> ret = PTR_ERR(kernel_type);
> if (IS_ERR(kernel_type))
> --
> 2.17.0
>