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SubjectRe: [patch 7/8] allow unprivileged mounts
Jan Engelhardt <> writes:

> On Apr 21 2007 08:10, Eric W. Biederman wrote:
>>>> Define a new fs flag FS_SAFE, which denotes, that unprivileged
>>>> mounting of this filesystem may not constitute a security problem.
>>>> Since most filesystems haven't been designed with unprivileged
>>>> mounting in mind, a thorough audit is needed before setting this flag.
>>> Practically speaking, is there any realistic likelihood that any filesystem
>>> apart from FUSE will ever use this?
>>Also potentially some of the kernel virtual filesystems. /proc should
>>be safe already. If you don't have any kind of backing store this problem
>>gets easier.
> tmpfs!

tmpfs is a possible problem because it can consume lots of ram/swap. Which
is why it has limits on the amount of space it can consume. Those are set as
mount options as I recall. Which means that we would need to do something
different with respect to limits before tmpfs could become safe for
an untrusted user to mount.

Still it's close.

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