From: Vivek Goyal <vgoyal@redhat.com>
To: "Daniel P. Berrangé" <berrange@redhat.com>
Cc: virtio-fs@redhat.com, vromanso@redhat.com, qemu-devel@nongnu.org,
stefanha@redhat.com, dgilbert@redhat.com
Subject: Re: [PATCH 2/5] virtiofsd: create lock/pid file in per user cache dir
Date: Thu, 30 Jul 2020 10:10:20 -0400 [thread overview]
Message-ID: <20200730141020.GA149245@redhat.com> (raw)
In-Reply-To: <20200730085937.GA3477223@redhat.com>
On Thu, Jul 30, 2020 at 09:59:37AM +0100, Daniel P. Berrangé wrote:
> On Wed, Jul 29, 2020 at 06:14:07PM -0400, Vivek Goyal wrote:
> > Right now we create lock/pid file in /usr/local/var/... and unprivliged
> > user does not have access to create files there.
> >
> > So create this file in per user cache dir as queried as specified
> > by environment variable XDG_RUNTIME_DIR.
> >
> > Note: "su $USER" does not update XDG_RUNTIME_DIR and it still points to
> > root user's director. So for now I create a directory /tmp/$UID to save
> > lock/pid file. Dan pointed out that it can be a problem if a malicious
> > app already has /tmp/$UID created. So we probably need to get rid of this.
>
> IMHO use of "su $USER" is simply user error and we don't need to
> care about workarounds. They will see the startup fail due to
> EPERM on /run/user/0 directory, and then they'll have to fix
> their command to use "su - $USER" to setup a clean environment.
I tried "su - $USER". That clears the old XDG_RUNTIME_DIR but does
not set new one. So now we have an empty XDG_RUNTIME_DIR env variable.
But good thing is that now g_get_user_runtime_dir() returns
"/home/$USER/.cache" and we can store user specific temp files there.
So I agree that I will get rid of all the logic to create /tmp/$USER.
"su $USER" will not be a supported path.
>
>
> > + /*
> > + * Unpriviliged users don't have access to /usr/local/var. Hence
> > + * store lock/pid file in per user directory. Use environment
> > + * variable XDG_RUNTIME_DIR.
> > + * If one logs into the system as root and then does "su" then
> > + * XDG_RUNTIME_DIR still points to root user directory. In that
> > + * case create a directory for user in /tmp/$UID
> > + */
> > + if (unprivileged) {
> > + gchar *user_dir = NULL;
> > + gboolean create_dir = false;
> > + user_dir = g_strdup(g_get_user_runtime_dir());
> > + if (!user_dir || g_str_has_suffix(user_dir, "/0")) {
> > + user_dir = g_strdup_printf("/tmp/%d", geteuid());
> > + create_dir = true;
> > + }
>
> As above, I don't think we need to have this fallback code to deal
> with something that is just user error.
>
> Also, g_get_user_runtime_dir() is guaranteed to return non-NULL.
Thanks. I will get rid of (!user_dir) case.
>
> > +
> > + if (create_dir && g_mkdir_with_parents(user_dir, S_IRWXU) < 0) {
> > + fuse_log(FUSE_LOG_ERR, "%s: Failed to create directory %s: %s",
> > + __func__, user_dir, strerror(errno));
> > + g_free(user_dir);
> > + return false;
> > + }
> > + dir = g_strdup(user_dir);
>
> Don't we also want to be appending "virtiofsd" to this directory path
> like we do in the privileged case ?
Yes. I forgot to append "virtiofsd" dir. Will do.
Thanks
Vivek
next prev parent reply other threads:[~2020-07-30 14:11 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-29 22:14 [RFC PATCH 0/5] virtiofsd: Add notion of unprivileged mode Vivek Goyal
2020-07-29 22:14 ` [PATCH 1/5] " Vivek Goyal
2020-07-29 22:14 ` [PATCH 2/5] virtiofsd: create lock/pid file in per user cache dir Vivek Goyal
2020-07-30 8:59 ` Daniel P. Berrangé
2020-07-30 14:10 ` Vivek Goyal [this message]
2020-07-29 22:14 ` [PATCH 3/5] virtiofsd: open /proc/self/fd/ in sandbox=NONE mode Vivek Goyal
2020-07-29 22:14 ` [PATCH 4/5] virtiofsd: Open lo->source while setting up root " Vivek Goyal
2020-07-29 22:14 ` [PATCH 5/5] virtiofsd: Skip setup_capabilities() " Vivek Goyal
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