linux-kernel - Re: Chromium sandbox on LoongArch and statx -- seccomp deep argument inspection again?

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Message-Id: <ef732971-bf70-4d8c-9fe8-3ca163a0c29c@app.fastmail.com>
Date: Mon, 26 Feb 2024 14:46:49 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "Christian Brauner" <brauner@...nel.org>
Cc: "Xi Ruoyao" <xry111@...111.site>, "Icenowy Zheng" <uwu@...nowy.me>,
 "Huacai Chen" <chenhuacai@...nel.org>, "WANG Xuerui" <kernel@...0n.name>,
 linux-api@...r.kernel.org, "Kees Cook" <keescook@...omium.org>,
 "Xuefeng Li" <lixuefeng@...ngson.cn>, "Jianmin Lv" <lvjianmin@...ngson.cn>,
 "Xiaotian Wu" <wuxiaotian@...ngson.cn>, "WANG Rui" <wangrui@...ngson.cn>,
 "Miao Wang" <shankerwangmiao@...il.com>,
 "loongarch@...ts.linux.dev" <loongarch@...ts.linux.dev>,
 Linux-Arch <linux-arch@...r.kernel.org>,
 "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: Chromium sandbox on LoongArch and statx -- seccomp deep argument
 inspection again?

On Mon, Feb 26, 2024, at 14:32, Christian Brauner wrote:
> On Mon, Feb 26, 2024 at 10:20:23AM +0100, Arnd Bergmann wrote:
>> On Mon, Feb 26, 2024, at 08:09, Xi Ruoyao wrote:
>
> What this tells me without knowing the exact reason is that they thought
> "Oh, if we just return ENOSYS then the workload or glibc will just
> always be able to fallback to fstat() or fstatat()". Which ultimately is
> the exact same thing that containers often assume.
>
> So really, just skipping on various system calls isn't going to work.
> You can't just implement new system calls and forget about the rest
> unless you know exactly what workloads your architecure will run on.
>
> Please implement fstat() or fstatat() and stop inventing hacks for
> statx() to make weird sandboxing rules work, please.

Do you mean we should add fstat64_time64() for all architectures
then? Would use use the same structure layout as statx for this,
the 64-bit version of the 'struct stat' layout from
include/uapi/asm-generic/stat.h, or something new that solves
the same problems?

I definitely don't want to see a new time32 API added to
mips64 and the 32-bit architectures, so the existing stat64
interface won't work as a statx replacement.

     Arnd