allow bind mounts outside of chroots
If we're in a unique namespace, there's no reason to not allow bind
mounts. These can be useful like when setting up a unique /dev, or
to make specific paths read-only for a daemon.
Bug: chromium:680859
Test: `sudo ./minijail0 -rvpd -b /dev/log,/dev/log /bin/logger asdf` works
Change-Id: I9dcb7f072dfdaee8b405e5d05e5d94ee999767e8
diff --git a/libminijail.c b/libminijail.c
index 0d83cb2..9ae1c87 100644
--- a/libminijail.c
+++ b/libminijail.c
@@ -192,6 +192,21 @@
static void run_hooks_or_die(const struct minijail *j,
minijail_hook_event_t event);
+static void free_mounts_list(struct minijail *j)
+{
+ while (j->mounts_head) {
+ struct mountpoint *m = j->mounts_head;
+ j->mounts_head = j->mounts_head->next;
+ free(m->data);
+ free(m->type);
+ free(m->dest);
+ free(m->src);
+ free(m);
+ }
+ // No need to clear mounts_head as we know it's NULL after the loop.
+ j->mounts_tail = NULL;
+}
+
/*
* Strip out flags meant for the parent.
* We keep things that are not inherited across execve(2) (e.g. capabilities),
@@ -228,6 +243,7 @@
if (j->suppl_gid_list)
free(j->suppl_gid_list);
j->suppl_gid_list = NULL;
+ free_mounts_list(j);
memset(&j->flags, 0, sizeof(j->flags));
/* Now restore anything we meant to keep. */
j->flags.vfs = vfs;
@@ -1145,15 +1161,7 @@
return 0;
bad_cgroups:
- while (j->mounts_head) {
- struct mountpoint *m = j->mounts_head;
- j->mounts_head = j->mounts_head->next;
- free(m->data);
- free(m->type);
- free(m->dest);
- free(m->src);
- free(m);
- }
+ free_mounts_list(j);
for (i = 0; i < j->cgroup_count; ++i)
free(j->cgroups[i]);
bad_mounts:
@@ -1356,7 +1364,7 @@
if (asprintf(&dest, "%s%s", dev_path, m->dest + 4) < 0)
return -ENOMEM;
} else {
- if (asprintf(&dest, "%s%s", j->chrootdir, m->dest) < 0)
+ if (asprintf(&dest, "%s%s", j->chrootdir ?: "", m->dest) < 0)
return -ENOMEM;
}
@@ -1399,20 +1407,35 @@
return ret;
}
-static int enter_chroot(const struct minijail *j, char *dev_path)
+static void process_mounts_or_die(const struct minijail *j)
{
- int ret;
+ /*
+ * We have to mount /dev first in case there are bind mounts from
+ * the original /dev into the new unique tmpfs one.
+ */
+ char *dev_path = NULL;
+ if (j->flags.mount_dev && mount_dev(&dev_path))
+ pdie("mount_dev failed");
- if (j->mounts_head && (ret = mount_one(j, j->mounts_head, dev_path)))
- return ret;
+ if (j->mounts_head && mount_one(j, j->mounts_head, dev_path)) {
+ if (dev_path) {
+ int saved_errno = errno;
+ mount_dev_cleanup(dev_path);
+ errno = saved_errno;
+ }
+ pdie("mount_one failed");
+ }
/*
- * Once all bind mounts have been processed, but before we chroot,
- * move the temp dev to its final /dev home.
+ * Once all bind mounts have been processed, move the temp dev to
+ * its final /dev home.
*/
if (j->flags.mount_dev && mount_dev_finalize(j, dev_path))
- return ret;
+ pdie("mount_dev_finalize failed");
+}
+static int enter_chroot(const struct minijail *j)
+{
run_hooks_or_die(j, MINIJAIL_HOOK_EVENT_PRE_CHROOT);
if (chroot(j->chrootdir))
@@ -1424,19 +1447,9 @@
return 0;
}
-static int enter_pivot_root(const struct minijail *j, char *dev_path)
+static int enter_pivot_root(const struct minijail *j)
{
- int ret, oldroot, newroot;
-
- if (j->mounts_head && (ret = mount_one(j, j->mounts_head, dev_path)))
- return ret;
-
- /*
- * Once all bind mounts have been processed, but before we pivot,
- * move the temp dev to its final /dev home.
- */
- if (j->flags.mount_dev && mount_dev_finalize(j, dev_path))
- return ret;
+ int oldroot, newroot;
run_hooks_or_die(j, MINIJAIL_HOOK_EVENT_PRE_CHROOT);
@@ -1970,33 +1983,14 @@
pdie("keyctl(KEYCTL_JOIN_SESSION_KEYRING) failed");
}
- /*
- * This has to come before the chroot/pivot_root in case there are
- * bind mounts from /dev into the chroot dev.
- */
- char *dev_path = NULL;
- if (j->flags.mount_dev && mount_dev(&dev_path))
- pdie("mount_dev");
+ /* We have to process all the mounts before we chroot/pivot_root. */
+ process_mounts_or_die(j);
- if (j->flags.chroot && enter_chroot(j, dev_path)) {
- if (dev_path)
- mount_dev_cleanup(dev_path);
+ if (j->flags.chroot && enter_chroot(j))
pdie("chroot");
- }
- if (j->flags.pivot_root && enter_pivot_root(j, dev_path)) {
- if (dev_path)
- mount_dev_cleanup(dev_path);
+ if (j->flags.pivot_root && enter_pivot_root(j))
pdie("pivot_root");
- }
-
- /*
- * If using a chroot or pivot root, we already finalized /dev at
- * the right point. If not, we need to call it ourselves.
- */
- if (j->flags.mount_dev && !j->flags.chroot && !j->flags.pivot_root &&
- mount_dev_finalize(j, dev_path))
- pdie("mount_dev_finalize");
if (j->flags.mount_tmp && mount_tmp(j))
pdie("mount_tmp");
@@ -2862,16 +2856,7 @@
free(j->filter_prog->filter);
free(j->filter_prog);
}
- while (j->mounts_head) {
- struct mountpoint *m = j->mounts_head;
- j->mounts_head = j->mounts_head->next;
- free(m->data);
- free(m->type);
- free(m->dest);
- free(m->src);
- free(m);
- }
- j->mounts_tail = NULL;
+ free_mounts_list(j);
while (j->hooks_head) {
struct hook *c = j->hooks_head;
j->hooks_head = c->next;