[Devel] Re: [patch] unprivileged mounts update

[H. Peter Anvin]

Miklos Szeredi wrote:
> 
> Andrew, please skip this patch, for now.
> 
> Serge found a problem with the fsuid approach: setfsuid(nonzero) will
> remove filesystem related capabilities.  So even if root is trying to
> set the "user=UID" flag on a mount, access to the target (and in case
> of bind, the source) is checked with user privileges.
> 
> Root should be able to set this flag on any mountpoint, _regardless_
> of permissions.
> 

Right, if you're using fsuid != 0, you're not running as root (fsuid is
the equivalent to euid for the filesystem.)

I fail to see how ruid should have *any* impact on mount(2).  That seems
to be a design flaw.

	-hpa
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