Date: Fri, 4 Feb 2022 10:45:15 +0100 From: Christian Brauner <brauner@...nel.org> To: "Anton V. Boyarshinov" <boyarsh@...linux.org> Cc: viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org, ebiederm@...ssion.com, legion@...nel.org, ldv@...linux.org, linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com, Christoph Hellwig <hch@....de>, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: [PATCH] Add ability to disallow idmapped mounts On Fri, Feb 04, 2022 at 09:53:38AM +0300, Anton V. Boyarshinov wrote: > Idmapped mounts may have security implications  and have > no knobs to be disallowed at runtime or compile time. > > This patch adds a sysctl and a config option to set its default value. > >  https://email@example.com/ > > Based on work from Alexey Gladkov <legion@...nel.org>. > > Signed-off-by: Anton V. Boyarshinov <boyarsh@...linux.org> > --- Thank your for the general idea, Anton. If you want to turn off idmapped mounts you can already do so today via: echo 0 > /proc/sys/user/max_user_namespaces Aside from that, idmapped mounts can only be created by fully privileged users on the host for a selected number of filesystems. They can neither be created as an unprivileged user nor can they be created inside user namespaces. I appreciate the worry. Any new feature may have security implications and bugs. In addition, we did address these allegations multiple times already (see , , , , ). As the author/maintainer of this feature, Nacked-by: Christian Brauner <brauner@...nel.org> : https://firstname.lastname@example.org/T/#m3a9df31aa183e8797c70bc193040adfd601399ad : https://email@example.com : https://firstname.lastname@example.org/T/#m59cdad9630d5a279aeecd0c1f117115144bc15eb : https://lore.kernel.org/lkml/20210510125147.tkgeurcindldiwxg@wittgenstein : https://lore.kernel.org/linux-fsdevel/CAHrFyr4AYi_gad7LQ-cJ9Peg=Gt73Sded8k_ZHeRZz=faGzpQA@mail.gmail.com
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