<p dir="ltr"><br>
---------- Forwarded message ----------<br>
From: "Christian Brauner" <<a href="mailto:christianvanbrauner@gmail.com">christianvanbrauner@gmail.com</a>><br>
Date: Oct 30, 2015 4:27 PM<br>
Subject: Re: [PATCH 2/2 v2] Update absolute paths for overlay and aufs mounts<br>
To: "Serge E. Hallyn" <<a href="mailto:serge.hallyn@ubuntu.com">serge.hallyn@ubuntu.com</a>><br>
Cc: "lxc-dev" <<a href="mailto:lxc-devel@lists.linuxcontainers.org">lxc-devel@lists.linuxcontainers.org</a>></p>
<p dir="ltr">><br>
> On Oct 30, 2015 4:22 PM, "Serge Hallyn" <<a href="mailto:serge.hallyn@ubuntu.com">serge.hallyn@ubuntu.com</a>> wrote:<br>
> ><br>
> > Quoting Christian Brauner (<a href="mailto:christianvanbrauner@gmail.com">christianvanbrauner@gmail.com</a>):<br>
> > > When using overlay and aufs mounts with lxc.mount.entry users have to specify<br>
> > > absolute paths for upperdir and workdir which will then get created<br>
> > > automatically by mount_entry_create_overlay_dirs() and<br>
> > > mount_entry_create_aufs_dirs() in conf.c. When we clone a container with<br>
> > > overlay or aufs lxc.mount.entry entries we need to update these absolute paths.<br>
> > > In order to do this we add the function update_union_mount_entry_paths() in<br>
> > > lxccontainer.c. The function updates the mounts in two locations:<br>
> > ><br>
> > > 1) lxc_conf->mount_list<br>
> > ><br>
> > > and<br>
> > ><br>
> > > 2) lxc_conf->unexpanded_config (by calling clone_update_unexp_ovl_dir())<br>
> > ><br>
> > > If we were to only update 2) we would end up with wrong upperdir and workdir<br>
> > > mounts as the absolute paths would still point to the container that serves as<br>
> > > the base for the clone. If we were to only update 1) we would end up with wrong<br>
> > > upperdir and workdir lxc.mount.entry entries in the clone's config as the<br>
> > > absolute paths in upperdir and workdir would still point to the container that<br>
> > > serves as the base for the clone. Updating both will get the job done.<br>
> > ><br>
> > > NOTE: This function does not sanitize paths apart from removing trailing<br>
> > > slashes. (So when a user specifies //home//someone/// it will be cleaned to<br>
> > > //home//someone. This is the minimal path cleansing which is also done by<br>
> > > lxc_container_new().) But the mount_entry_create_overlay_dirs() and<br>
> > > mount_entry_create_aufs_dirs() functions both try to be extremely strict about<br>
> > > when to create upperdirs and workdirs. They will only accept sanitized paths,<br>
> > > i.e. they require /home/someone. I think this is a (safety) virtue and we<br>
> > > should consider sanitizing paths in general. In short:<br>
> > > update_union_mount_entry_paths() does update all absolute paths to the new<br>
> > > container but mount_entry_create_overlay_dirs() and<br>
> > > mount_entry_create_aufs_dirs() will still refuse to create upperdir and workdir<br>
> > > when the updated path is unclean. This happens easily when e.g. a user calls<br>
> > > lxc-clone -o OLD -n NEW -P //home//chb///.<br>
> > ><br>
> > > Signed-off-by: Christian Brauner <<a href="mailto:christianvanbrauner@gmail.com">christianvanbrauner@gmail.com</a>><br>
> ><br>
> > Acked-by: Serge E. Hallyn <<a href="mailto:serge.hallyn@ubuntu.com">serge.hallyn@ubuntu.com</a>><br>
> ><br>
> > > ---<br>
> > > src/lxc/lxccontainer.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++<br>
> > > 1 file changed, 97 insertions(+)<br>
> > ><br>
> > > diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c<br>
> > > index 42e23e7..8edf6a2 100644<br>
> > > --- a/src/lxc/lxccontainer.c<br>
> > > +++ b/src/lxc/lxccontainer.c<br>
> > > @@ -2894,6 +2894,99 @@ static int create_file_dirname(char *path, struct lxc_conf *conf)<br>
> > > return ret;<br>
> > > }<br>
> > ><br>
> > > +/* When we clone a container with overlay or aufs lxc.mount.entry entries we<br>
> > > +* need to update these absolute paths. In order to do this we add the function<br>
> > > +* update_union_mount_entry_paths() in lxccontainer.c. The function operates on<br>
> > > +* c->lxc_conf->unexpanded_config instead of the intuitively plausible<br>
> > > +* c->lxc_conf->mount_list because the latter also contains mounts from other<br>
> > > +* files as well as generic mounts. */<br>
> > > +static int update_union_mount_entry_paths(struct lxc_conf *lxc_conf,<br>
> > > + const char *lxc_path,<br>
> > > + const char *lxc_name,<br>
> > > + const char *newpath,<br>
> > > + const char *newname)<br>
> > > +{<br>
> > > + char new_upper[MAXPATHLEN];<br>
> > > + char new_work[MAXPATHLEN];<br>
> > > + char old_upper[MAXPATHLEN];<br>
> > > + char old_work[MAXPATHLEN];<br>
> > > + char *cleanpath = NULL;<br>
> > > + int i;<br>
> > > + int fret = -1;<br>
> > > + int ret = 0;<br>
> > > + struct lxc_list *iterator;<br>
> > > + const char *ovl_dirs[] = {"br", "upperdir", "workdir"};<br>
> > > +<br>
> > > + cleanpath = strdup(newpath);<br>
> > > + if (!cleanpath)<br>
> > > + goto err;<br>
> > > +<br>
> > > + remove_trailing_slashes(cleanpath);<br>
> > > +<br>
> ><br>
> > Would be wortha comment here saying "we have to update the unexpanded<br>
> > configuration separately from the expanded one."</p>
<p dir="ltr">I can insert it, add your Acked-by line to the cover letter and leave a short reminder in the cover letter that I only inserted a comment per your request so you know what's going on. Ok?</p>
<p dir="ltr">> ><br>
> > > + for (i = 0; i < sizeof(ovl_dirs) / sizeof(ovl_dirs[0]); i++) {<br>
> > > + if (!clone_update_unexp_ovl_dir(lxc_conf, lxc_path, newpath,<br>
> > > + lxc_name, newname, ovl_dirs[i]))<br>
> > > + goto err;<br>
> > > + }<br>
> > > +<br>
> > > + ret = snprintf(old_work, MAXPATHLEN, "workdir=%s/%s", lxc_path, lxc_name);<br>
> > > + if (ret < 0 || ret >= MAXPATHLEN)<br>
> > > + goto err;<br>
> > > +<br>
> > > + ret = snprintf(new_work, MAXPATHLEN, "workdir=%s/%s", cleanpath, newname);<br>
> > > + if (ret < 0 || ret >= MAXPATHLEN)<br>
> > > + goto err;<br>
> > > +<br>
> > > + lxc_list_for_each(iterator, &lxc_conf->mount_list) {<br>
> > > + char *mnt_entry = NULL;<br>
> > > + char *new_mnt_entry = NULL;<br>
> > > + char *tmp = NULL;<br>
> > > + char *tmp_mnt_entry = NULL;<br>
> > > + mnt_entry = iterator->elem;<br>
> > > +<br>
> > > + if (strstr(mnt_entry, "overlay"))<br>
> > > + tmp = "upperdir";<br>
> > > + else if (strstr(mnt_entry, "aufs"))<br>
> > > + tmp = "br";<br>
> > > +<br>
> > > + if (!tmp)<br>
> > > + continue;<br>
> > > +<br>
> > > + ret = snprintf(old_upper, MAXPATHLEN, "%s=%s/%s", tmp, lxc_path, lxc_name);<br>
> > > + if (ret < 0 || ret >= MAXPATHLEN)<br>
> > > + goto err;<br>
> > > +<br>
> > > + ret = snprintf(new_upper, MAXPATHLEN, "%s=%s/%s", tmp, cleanpath, newname);<br>
> > > + if (ret < 0 || ret >= MAXPATHLEN)<br>
> > > + goto err;<br>
> > > +<br>
> > > + if (strstr(mnt_entry, old_upper)) {<br>
> > > + tmp_mnt_entry = lxc_string_replace(old_upper, new_upper, mnt_entry);<br>
> > > + }<br>
> > > +<br>
> > > + if (strstr(mnt_entry, old_work)) {<br>
> > > + if (tmp_mnt_entry)<br>
> > > + new_mnt_entry = lxc_string_replace(old_work, new_work, tmp_mnt_entry);<br>
> > > + }<br>
> > > +<br>
> > > + if (new_mnt_entry) {<br>
> > > + free(iterator->elem);<br>
> > > + iterator->elem = strdup(new_mnt_entry);<br>
> > > + } else if (tmp_mnt_entry) {<br>
> > > + free(iterator->elem);<br>
> > > + iterator->elem = strdup(tmp_mnt_entry);<br>
> > > + }<br>
> > > +<br>
> > > + free(new_mnt_entry);<br>
> > > + free(tmp_mnt_entry);<br>
> > > + }<br>
> > > +<br>
> > > + fret = 0;<br>
> > > +err:<br>
> > > + free(cleanpath);<br>
> > > + return fret;<br>
> > > +}<br>
> > > +<br>
> > > static struct lxc_container *do_lxcapi_clone(struct lxc_container *c, const char *newname,<br>
> > > const char *lxcpath, int flags,<br>
> > > const char *bdevtype, const char *bdevdata, uint64_t newsize,<br>
> > > @@ -3009,6 +3102,10 @@ static struct lxc_container *do_lxcapi_clone(struct lxc_container *c, const char<br>
> > > }<br>
> > > }<br>
> > ><br>
> > > + // update absolute paths for union mount directories<br>
> > > + if (update_union_mount_entry_paths(c2->lxc_conf, c->config_path, c->name, lxcpath, newname) < 0)<br>
> > > + goto out;<br>
> > > +<br>
> > > // We've now successfully created c2's storage, so clear it out if we<br>
> > > // fail after this<br>
> > > storage_copied = 1;<br>
> > > --<br>
> > > 2.6.2<br>
> > ><br>
</p>