Re: [PATCH 4/6] fuse: enable close_wait synchronous release

[Maxim Patlasov]

On 08/22/2014 06:04 PM, Miklos Szeredi wrote:
> On Thu, Aug 21, 2014 at 6:09 PM, Maxim Patlasov <MPatlasov@xxxxxxxxxxxxx> wrote:
> > The patch enables the feature by passing 'true' to fuse_file_put in
> > fuse_release_common.
> >
> > Previously, this was safe only in special cases when we sure that
> > multi-threaded userspace won't deadlock if we'll synchronously send
> > FUSE_RELEASE in the context of read-ahead or write-back callback. Now, it's
> > always safe because callbacks don't send requests to userspace anymore.
> But we do want to make this privileged, as there are unlikely but
> possible DoS scenarios with a sync release.

The latest patch of the set implements DISABLE_SYNC_RELEASE mount 
option. We can instrument fusermount to use the option by default for 
unprivileged mounts (allowing system administrator to configure it like 
"user_allow_other"). Do you have a better way to implement DoS 
protection in mind?

Thanks,
Maxim
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