linux-kernel - Re: [PATCH] device_cgroup: Cleanup cgroup eBPF device filter code

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Message-ID: <20200403223704.GA306670@carbon.dhcp.thefacebook.com>
Date:   Fri, 3 Apr 2020 15:37:04 -0700
From:   Roman Gushchin <guro@...com>
To:     Odin Ugedal <odin@...dal.com>
CC:     <bpf@...r.kernel.org>, <linux-security-module@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <tj@...nel.org>,
        <Harish.Kasiviswanathan@....com>, <amd-gfx@...ts.freedesktop.org>
Subject: Re: [PATCH] device_cgroup: Cleanup cgroup eBPF device filter code

On Fri, Apr 03, 2020 at 07:55:28PM +0200, Odin Ugedal wrote:
> Original cgroup v2 eBPF code for filtering device access made it
> possible to compile with CONFIG_CGROUP_DEVICE=n and still use the eBPF
> filtering. Change 
> commit 4b7d4d453fc4 ("device_cgroup: Export devcgroup_check_permission")
> reverted this, making it required to set it to y.
> 
> Since the device filtering (and all the docs) for cgroup v2 is no longer
> a "device controller" like it was in v1, someone might compile their
> kernel with CONFIG_CGROUP_DEVICE=n. Then (for linux 5.5+) the eBPF
> filter will not be invoked, and all processes will be allowed access
> to all devices, no matter what the eBPF filter says.
> 
> Signed-off-by: Odin Ugedal <odin@...dal.com>

Hello, Odin!

The patch makes perfect sense to me.

Acked-by: Roman Gushchin <guro@...com>

Thanks!