Quoting Christian Brauner (christianvanbrau...@gmail.com):
> The mount_entry_overlay_dirs() and mount_entry_aufs_dirs() functions create
> workdirs and upperdirs for overlay and aufs lxc.mount.entry entries. They try
> to make sure that the workdirs and upperdirs can only be created under the
> containerdir (e.g. /path/to/the/container/CONTAINERNAME). In order to do this
> the right hand side of
>
> if ((strncmp(upperdir, lxcpath, dirlen) == 0) &&
> (strncmp(upperdir, rootfs->path, rootfslen) != 0))
>
> was thought to check if the rootfs->path is not present in the workdir and
> upperdir mount options. But the current check is bogus since it will be
> trivially true whenever the container is a block-dev or overlay or aufs backed
> since the rootfs->path will then have a form like e.g.
>
> overlayfs:/some/path:/some/other/path
>
> This patch parses rootfs->path by searching backwards for the first occurrence
> of the delimiter pair ":/". We do not simply search for ":" since it might be
> used in path names.
>
> Signed-off-by: Christian Brauner <christianvanbrau...@gmail.com>
> ---
> src/lxc/conf.c | 126
> ++++++++++++++++++++++++++++++++++++++++++++++-----------
> 1 file changed, 103 insertions(+), 23 deletions(-)
>
> diff --git a/src/lxc/conf.c b/src/lxc/conf.c
> index 16a62f8..a730a67 100644
> --- a/src/lxc/conf.c
> +++ b/src/lxc/conf.c
> @@ -1821,6 +1821,11 @@ static int mount_entry_create_overlay_dirs(const
> struct mntent *mntent,
> const char *lxc_path)
> {
> char lxcpath[MAXPATHLEN];
> + char *end = NULL;
> + char *rootfsdir = NULL;
> + char *s = NULL;
> + char *s1 = NULL;
> + char *tmp = NULL;
> char *upperdir = NULL;
> char *workdir = NULL;
> char **opts = NULL;
> @@ -1830,15 +1835,16 @@ static int mount_entry_create_overlay_dirs(const
> struct mntent *mntent,
> size_t i;
> size_t len = 0;
> size_t rootfslen = 0;
> + size_t slen = 0;
>
> if (!rootfs->path || !lxc_name || !lxc_path)
> - return -1;
> + goto err;
>
> opts = lxc_string_split(mntent->mnt_opts, ',');
> if (opts)
> arrlen = lxc_array_len((void **)opts);
> else
> - return -1;
> + goto err;
>
> for (i = 0; i < arrlen; i++) {
> if (strstr(opts[i], "upperdir=") && (strlen(opts[i]) > (len =
> strlen("upperdir="))))
> @@ -1848,31 +1854,66 @@ static int mount_entry_create_overlay_dirs(const
> struct mntent *mntent,
> }
>
> ret = snprintf(lxcpath, MAXPATHLEN, "%s/%s", lxc_path, lxc_name);
> - if (ret < 0 || ret >= MAXPATHLEN) {
> - lxc_free_array((void **)opts, free);
> - return -1;
> - }
> + if (ret < 0 || ret >= MAXPATHLEN)
> + goto err;
>
> dirlen = strlen(lxcpath);
> - rootfslen = strlen(rootfs->path);
> +
Could you put this stuff into a helper, i.e.
rootfsdir = ovl_get_rootfs_dir(rootfs->path, &rootfslen);
> + s = strdup(rootfs->path);
> + if (!s)
> + goto err;
> +
> + s1 = malloc(strlen(rootfs->path) + 1);
> + if (!s1)
> + goto err;
> + end = stpcpy(s1, rootfs->path);
> +
> + /* If we find :/ in rootfs->path it means we either have a block-dev or
> + * overlay or aufs container. */
> + while ((tmp = strrchr(s, ':'))) {
> + len = strlen(tmp);
> + rootfslen += len;
> + if (strncmp(tmp, ":/", 2) == 0) {
> + rootfsdir = end - rootfslen + 1;
> + rootfslen = strlen(rootfsdir);
> + break;
> + } else {
> + slen = strlen(s);
> + s[slen - len] = '\0';
> + }
> + }
> +
> + /* If rootfsdir is empty at this point we have a simple directory
> + * container. */
> + if (!rootfsdir) {
> + rootfsdir = rootfs->path;
> + rootfslen = strlen(rootfs->path);
> + }
>
> /* We neither allow users to create upperdirs and workdirs outside the
> * containerdir nor inside the rootfs. The latter might be debatable. */
> if (upperdir)
> - if ((strncmp(upperdir, lxcpath, dirlen) == 0) &&
> (strncmp(upperdir, rootfs->path, rootfslen) != 0))
> + if ((strncmp(upperdir, lxcpath, dirlen) == 0) &&
> (strncmp(upperdir, rootfsdir, rootfslen) != 0))
> if (mkdir_p(upperdir, 0755) < 0) {
> WARN("Failed to create upperdir");
> }
>
>
> if (workdir)
> - if ((strncmp(workdir, lxcpath, dirlen) == 0) &&
> (strncmp(workdir, rootfs->path, rootfslen) != 0))
> + if ((strncmp(workdir, lxcpath, dirlen) == 0) &&
> (strncmp(workdir, rootfsdir, rootfslen) != 0))
> if (mkdir_p(workdir, 0755) < 0) {
> WARN("Failed to create workdir");
> }
>
> + free(s);
> + free(s1);
> lxc_free_array((void **)opts, free);
> return 0;
> +err:
> + free(s);
> + free(s1);
> + lxc_free_array((void **)opts, free);
> + return -1;
> }
>
> static int mount_entry_create_aufs_dirs(const struct mntent *mntent,
> @@ -1881,6 +1922,10 @@ static int mount_entry_create_aufs_dirs(const struct
> mntent *mntent,
> const char *lxc_path)
> {
> char lxcpath[MAXPATHLEN];
> + char *end = NULL;
> + char *rootfsdir = NULL;
> + char *s = NULL;
> + char *s1 = NULL;
> char *scratch = NULL;
> char *tmp = NULL;
> char *upperdir = NULL;
> @@ -1889,44 +1934,79 @@ static int mount_entry_create_aufs_dirs(const struct
> mntent *mntent,
> size_t arrlen = 0;
> size_t i;
> size_t len = 0;
> + size_t rootfslen = 0;
> + size_t slen = 0;
>
> if (!rootfs->path || !lxc_name || !lxc_path)
> - return -1;
> + goto err;
>
> opts = lxc_string_split(mntent->mnt_opts, ',');
> if (opts)
> arrlen = lxc_array_len((void **)opts);
> else
> - return -1;
> + goto err;
>
> for (i = 0; i < arrlen; i++) {
> if (strstr(opts[i], "br=") && (strlen(opts[i]) > (len =
> strlen("br="))))
> tmp = opts[i] + len;
> }
> - if (!tmp) {
> - lxc_free_array((void **)opts, free);
> - return -1;
> - }
> + if (!tmp)
> + goto err;
>
> upperdir = strtok_r(tmp, ":=", &scratch);
> - if (!upperdir) {
> - lxc_free_array((void **)opts, free);
> - return -1;
> - }
> + if (!upperdir)
> + goto err;
>
> ret = snprintf(lxcpath, MAXPATHLEN, "%s/%s", lxc_path, lxc_name);
> - if (ret < 0 || ret >= MAXPATHLEN) {
> - lxc_free_array((void **)opts, free);
> - return -1;
> + if (ret < 0 || ret >= MAXPATHLEN)
> + goto err;
> +
> + s = strdup(rootfs->path);
> + if (!s)
> + goto err;
> +
> + s1 = malloc(strlen(rootfs->path) + 1);
> + if (!s1)
> + goto err;
> + end = stpcpy(s1, rootfs->path);
> +
> + /* If we find :/ in rootfs->path it means we either have a block-dev or
> + * overlay or aufs container. */
> + while ((tmp = strrchr(s, ':'))) {
> + len = strlen(tmp);
> + rootfslen += len;
> + if (strncmp(tmp, ":/", 2) == 0) {
> + rootfsdir = end - rootfslen + 1;
> + rootfslen = strlen(rootfsdir);
> + break;
> + } else {
> + slen = strlen(s);
> + s[slen - len] = '\0';
> + }
> + }
> +
> + /* If rootfsdir is empty at this point we have a simple directory
> + * container. */
> + if (!rootfsdir) {
> + rootfsdir = rootfs->path;
> + rootfslen = strlen(rootfs->path);
> }
>
> /* We neither allow users to create upperdirs outside the containerdir
> * nor inside the rootfs. The latter might be debatable. */
> - if ((strncmp(upperdir, lxcpath, strlen(lxcpath)) == 0) &&
> (strncmp(upperdir, rootfs->path, strlen(rootfs->path)) != 0))
> + if ((strncmp(upperdir, lxcpath, strlen(lxcpath)) == 0) &&
> (strncmp(upperdir, rootfsdir, rootfslen) != 0))
> if (mkdir_p(upperdir, 0755) < 0) {
> WARN("Failed to create upperdir");
> }
>
> + free(s);
> + free(s1);
> + lxc_free_array((void **)opts, free);
> + return 0;
> +
> +err:
> + free(s);
> + free(s1);
> lxc_free_array((void **)opts, free);
> return 0;
> }
> --
> 2.6.1
>
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