jail: make use of realpath() for rootfs and overlaydir

Use realpath() to resolve rootfs and read/write-overlay as they are
potentially (and likely, as we are going to use blockd with autofs)
symlinks.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

diff --git a/jail/jail.c b/jail/jail.c
index 4cc16c8a9bb9ac5319dac63934dd3ad8b180cfbc..e6c908112c6d174e9b886f64fd69c7552f8b9bff 100644 (file)
--- a/jail/jail.c
+++ b/jail/jail.c
@@ -621,6 +621,7 @@ static void enter_jail_fs(void);
 static int build_jail_fs(void)
 {
        char *overlaydir = NULL;
+       int ret;
 
        old_umask = umask(0);
 
@@ -641,7 +642,7 @@ static int build_jail_fs(void)
        }
 
        if (opts.extroot) {
-               /* use stat to trigger autofs mount */
+               /* use open() to trigger autofs mount */
                DEBUG("mounting extroot from %s\n", opts.extroot);
                int rootdirfd = open(opts.extroot, O_RDONLY | O_DIRECTORY);
                if (rootdirfd == -1) {
@@ -674,14 +675,23 @@ static int build_jail_fs(void)
                        ERROR("failed to mount tmpfs for overlay (size=%s)\n", opts.tmpoverlaysize);
                        return -1;
                }
-               overlaydir = tmpovdir;
+               overlaydir = strdup(tmpovdir);
+               if (!overlaydir)
+                       return -1;
        }
 
-       if (opts.overlaydir)
-               overlaydir = opts.overlaydir;
+       if (opts.overlaydir) {
+               overlaydir = realpath(opts.overlaydir, NULL);
+               if (!overlaydir)
+                       return errno;
+       }
 
-       if (overlaydir)
-               mount_overlay(jail_root, overlaydir);
+       if (overlaydir) {
+               ret = mount_overlay(jail_root, overlaydir);
+               free(overlaydir);
+               if (ret)
+                       return ret;
+       }
 
        if (chdir(jail_root)) {
                ERROR("chdir(%s) (jail_root) failed: %m\n", jail_root);
@@ -1332,9 +1342,7 @@ static const struct blobmsg_policy oci_root_policy[] = {
 
 static int parseOCIroot(const char *jsonfile, struct blob_attr *msg)
 {
-       static char extroot[PATH_MAX] = { 0 };
-       char buf[PATH_MAX];
-       ssize_t len;
+       char extroot[PATH_MAX] = { 0 };
        struct blob_attr *tb[__OCI_ROOT_MAX];
        char *cur;
        char *root_path;
@@ -1360,21 +1368,9 @@ static int parseOCIroot(const char *jsonfile, struct blob_attr *msg)
        strncat(extroot, root_path, PATH_MAX - (strlen(extroot) + 1));
 
        /* follow symbolic link(s) */
-       while ((len = readlink(extroot, buf, sizeof(buf)-1)) != -1) {
-               buf[len] = '\0';
-               if (buf[0] != '/') {
-                       cur = strrchr(extroot, '/');
-                       if (!cur)
-                               return ENOTDIR;
-
-                       *(++cur) = '\0';
-                       strncat(extroot, buf, sizeof(extroot)-1);
-               } else {
-                       strncpy(extroot, buf, sizeof(extroot)-1);
-               }
-       }
-
-       opts.extroot = extroot;
+       opts.extroot = realpath(extroot, NULL);
+       if (!opts.extroot)
+               return errno;
 
        if (tb[OCI_ROOT_READONLY])
                opts.ronly = blobmsg_get_bool(tb[OCI_ROOT_READONLY]);