netdev - Re: [PATCH bpf-next] bpf: comment why dots in filenames under BPF virtual FS are not allowed

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Date:   Fri, 9 Mar 2018 10:32:18 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>,
        alexei.starovoitov@...il.com
Cc:     netdev@...r.kernel.org, oss-drivers@...ronome.com,
        Quentin Monnet <quentin.monnet@...ronome.com>
Subject: Re: [PATCH bpf-next] bpf: comment why dots in filenames under BPF
 virtual FS are not allowed

On 03/09/2018 08:46 AM, Jakub Kicinski wrote:
> From: Quentin Monnet <quentin.monnet@...ronome.com>
> 
> When pinning a file under the BPF virtual file system (traditionally
> /sys/fs/bpf), using a dot in the name of the location to pin at is not
> allowed. For example, trying to pin at "/sys/fs/bpf/foo.bar" will be
> rejected with -EPERM.
> 
> This check was introduced at the same time as the BPF file system
> itself, with commit b2197755b263 ("bpf: add support for persistent
> maps/progs"). At this time, it was checked in a function called
> "bpf_dname_reserved()", which made clear that using a dot was reserved
> for future extensions.
> 
> This function disappeared and the check was moved elsewhere with commit
> 0c93b7d85d40 ("bpf: reject invalid names right in ->lookup()"), and the
> meaning of the dot ban was lost.
> 
> The present commit simply adds a comment in the source to explain to the
> reader that the usage of dots is reserved for future usage.
> 
> Signed-off-by: Quentin Monnet <quentin.monnet@...ronome.com>

Applied to bpf-next, thanks Quentin!