linux-kernel - Re: [PATCH 15/17] file: In f_dupfd read RLIMIT

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Message-ID: <20200818101226.weamow3swms6xizm@wittgenstein>
Date:   Tue, 18 Aug 2020 12:12:26 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        criu@...nvz.org, bpf@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Oleg Nesterov <oleg@...hat.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Jann Horn <jann@...jh.net>, Kees Cook <keescook@...omium.org>,
        Daniel P. Berrangé <berrange@...hat.com>,
        Jeff Layton <jlayton@...hat.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        Matthew Wilcox <willy@...ian.org>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Matthew Wilcox <matthew@....cx>,
        Trond Myklebust <trond.myklebust@....uio.no>,
        Chris Wright <chrisw@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>
Subject: Re: [PATCH 15/17] file: In f_dupfd read RLIMIT_NOFILE once.

On Mon, Aug 17, 2020 at 05:04:23PM -0500, Eric W. Biederman wrote:
> Simplify the code, and remove the chance of races by reading
> RLIMIT_NOFILE only once in f_dupfd.
> 
> Pass the read value of RLIMIT_NOFILE into alloc_fd which is the other
> location the rlimit was read in f_dupfd.  As f_dupfd is the only
> caller of alloc_fd this changing alloc_fd is trivially safe.
> 
> Further this causes alloc_fd to take all of the same arguments as
> __alloc_fd except for the files_struct argument.
> 
> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
> ---

Acked-by: Christian Brauner <christian.brauner@...ntu.com>