linux-kernel - Re: [PATCH v10 1/9] mm: Introduce memfd_restricted system call to create restricted user memory

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <diqzh6tjofy3.fsf@ackerleytng-cloudtop.c.googlers.com>
Date:   Thu, 13 Apr 2023 17:22:12 +0000
From:   Ackerley Tng <ackerleytng@...gle.com>
To:     Chao Peng <chao.p.peng@...ux.intel.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        linux-doc@...r.kernel.org, qemu-devel@...gnu.org,
        pbonzini@...hat.com, corbet@....net, seanjc@...gle.com,
        vkuznets@...hat.com, wanpengli@...cent.com, jmattson@...gle.com,
        joro@...tes.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, arnd@...db.de, naoya.horiguchi@....com,
        linmiaohe@...wei.com, x86@...nel.org, hpa@...or.com,
        hughd@...gle.com, jlayton@...nel.org, bfields@...ldses.org,
        akpm@...ux-foundation.org, shuah@...nel.org, rppt@...nel.org,
        steven.price@....com, mail@...iej.szmigiero.name, vbabka@...e.cz,
        vannapurve@...gle.com, yu.c.zhang@...ux.intel.com,
        chao.p.peng@...ux.intel.com, kirill.shutemov@...ux.intel.com,
        luto@...nel.org, jun.nakajima@...el.com, dave.hansen@...el.com,
        ak@...ux.intel.com, david@...hat.com, aarcange@...hat.com,
        ddutile@...hat.com, dhildenb@...hat.com, qperret@...gle.com,
        tabba@...gle.com, michael.roth@....com, mhocko@...e.com,
        wei.w.wang@...el.com
Subject: Re: [PATCH v10 1/9] mm: Introduce memfd_restricted system call to
 create restricted user memory

Chao Peng <chao.p.peng@...ux.intel.com> writes:

> From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>

> Introduce 'memfd_restricted' system call with the ability to create
> memory areas that are restricted from userspace access through ordinary
> MMU operations (e.g. read/write/mmap). The memory content is expected to
> be used through the new in-kernel interface by a third kernel module.

> ...

> diff --git a/mm/restrictedmem.c b/mm/restrictedmem.c
> new file mode 100644
> index 000000000000..56953c204e5c
> --- /dev/null
> +++ b/mm/restrictedmem.c
> @@ -0,0 +1,318 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include "linux/sbitmap.h"
> +#include <linux/pagemap.h>
> +#include <linux/pseudo_fs.h>
> +#include <linux/shmem_fs.h>
> +#include <linux/syscalls.h>
> +#include <uapi/linux/falloc.h>
> +#include <uapi/linux/magic.h>
> +#include <linux/restrictedmem.h>
> +
> +struct restrictedmem_data {
> +	struct mutex lock;
> +	struct file *memfd;

Can this be renamed to file, or lower_file (as in stacking filesystems)?

It's a little confusing because this pointer doesn't actually refer to
an fd.

'memfd' is already used by udmabuf to refer to an actual fd [1], which
makes this a little misleading.

[1]  
https://elixir.bootlin.com/linux/v6.2.10/source/tools/testing/selftests/drivers/dma-buf/udmabuf.c#L63

> +	struct list_head notifiers;
> +};
> +
> ...