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Re: [PATCH 2/5] virtiofsd: create lock/pid file in per user cache dir
From: |
Daniel P . Berrangé |
Subject: |
Re: [PATCH 2/5] virtiofsd: create lock/pid file in per user cache dir |
Date: |
Thu, 30 Jul 2020 09:59:37 +0100 |
User-agent: |
Mutt/1.14.5 (2020-06-23) |
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 - $USER" to setup a clean environment.
> + /*
> + * Unpriviliged users don't have access to /usr/local/var. Hence
> + * store lock/pid file in per user directory. Use environment
> + * variable XDG_RUNTIME_DIR.
> + * If one logs into the system as root and then does "su" then
> + * XDG_RUNTIME_DIR still points to root user directory. In that
> + * case create a directory for user in /tmp/$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.
> +
> + 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 ?
> + g_free(user_dir);
> + } else {
> + dir = qemu_get_local_state_pathname("run/virtiofsd");
> + if (g_mkdir_with_parents(dir, S_IRWXU) < 0) {
> + fuse_log(FUSE_LOG_ERR, "%s: Failed to create directory %s: %s",
> + __func__, dir, strerror(errno));
> + return false;
> + }
> }
>
> sk_name = g_strdup(se->vu_socket_path);
> --
> 2.25.4
>
Regards,
Daniel
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- [RFC PATCH 0/5] virtiofsd: Add notion of unprivileged mode, Vivek Goyal, 2020/07/29
- [PATCH 1/5] virtiofsd: Add notion of unprivileged mode, Vivek Goyal, 2020/07/29
- [PATCH 2/5] virtiofsd: create lock/pid file in per user cache dir, Vivek Goyal, 2020/07/29
- Re: [PATCH 2/5] virtiofsd: create lock/pid file in per user cache dir,
Daniel P . Berrangé <=
- [PATCH 4/5] virtiofsd: Open lo->source while setting up root in sandbox=NONE mode, Vivek Goyal, 2020/07/29
- [PATCH 3/5] virtiofsd: open /proc/self/fd/ in sandbox=NONE mode, Vivek Goyal, 2020/07/29
- [PATCH 5/5] virtiofsd: Skip setup_capabilities() in sandbox=NONE mode, Vivek Goyal, 2020/07/29