linux-kernel - Re: [PATCH] vhost: vringh: Use matching allocation type in resize

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Message-ID: <CACGkMEtPmDBsyHTsAMZ7aygPQ1CVELd8H4_1u4ySH4sMQXe=qw@mail.gmail.com>
Date: Tue, 29 Apr 2025 11:37:03 +0800
From: Jason Wang <jasowang@...hat.com>
To: Kees Cook <kees@...nel.org>
Cc: "Michael S. Tsirkin" <mst@...hat.com>, Eugenio Pérez <eperezma@...hat.com>, 
	kvm@...r.kernel.org, virtualization@...ts.linux.dev, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] vhost: vringh: Use matching allocation type in resize_iovec()

On Sat, Apr 26, 2025 at 2:22 PM Kees Cook <kees@...nel.org> wrote:
>
> In preparation for making the kmalloc family of allocators type aware,
> we need to make sure that the returned type from the allocation matches
> the type of the variable being assigned. (Before, the allocator would
> always return "void *", which can be implicitly cast to any pointer type.)
>
> The assigned type is "struct kvec *", but the returned type will be
> "struct iovec *". These have the same allocation size, so there is no
> bug:
>
> struct kvec {
>         void *iov_base; /* and that should *never* hold a userland pointer */
>         size_t iov_len;
> };
>
> struct iovec
> {
>         void __user *iov_base;  /* BSD uses caddr_t (1003.1g requires void *) */
>         __kernel_size_t iov_len; /* Must be size_t (1003.1g) */
> };
>
> Adjust the allocation type to match the assignment.
>
> Signed-off-by: Kees Cook <kees@...nel.org>

Acked-by: Jason Wang <jasowang@...hat.com>

Thanks