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

From: Xi Ruoyao <xry111@xry111.site>
To: WANG Xuerui <kernel@xen0n.name>, linux-api@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>,
	Christian Brauner <brauner@kernel.org>,
	 Kees Cook <keescook@chromium.org>,
	Huacai Chen <chenhuacai@kernel.org>,
	Xuefeng Li <lixuefeng@loongson.cn>,
	Jianmin Lv <lvjianmin@loongson.cn>,
	Xiaotian Wu <wuxiaotian@loongson.cn>,
	WANG Rui <wangrui@loongson.cn>,
	Miao Wang <shankerwangmiao@gmail.com>,
	Icenowy Zheng <uwu@icenowy.me>,
	 "loongarch@lists.linux.dev" <loongarch@lists.linux.dev>,
	linux-arch <linux-arch@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Chromium sandbox on LoongArch and statx -- seccomp deep argument inspection again?
Date: Wed, 21 Feb 2024 18:31:46 +0800	[thread overview]
Message-ID: <2d25e3bb829cbca51387eb84985db919f50ccd37.camel@xry111.site> (raw)
In-Reply-To: <f1a1bc708be543eb647df57b5eb0c0ef035baf8b.camel@xry111.site>

On Wed, 2024-02-21 at 14:31 +0800, Xi Ruoyao wrote:
> On Wed, 2024-02-21 at 14:09 +0800, WANG Xuerui wrote:
> 
> > - just restore fstat and be done with it;
> > - add a flag to statx so we can do the equivalent of just fstat(fd, 
> > &out) with statx, and ensuring an error happens if path is not empty in 
> > that case;
> 
> It's worse than "just restore fstat" considering the performance.  Read
> this thread:
> https://sourceware.org/pipermail/libc-alpha/2023-September/151320.html

Hmm, but it looks like statx already suffers the same performance issue.
And in this libc-alpha discussion Linus said:

   If the user asked for 'fstat()', just give the user 'fstat()'.

So to me we should just add fstat (and use it in Glibc for LoongArch, only
falling back to statx if fstat returns -ENOSYS), or am I missing something?

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University