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chrootenv: propagate nested chrootenv /host

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To avoid symlink loops to /host in nested chrootenvs we need to remove
one level of indirection. This is also what's generally expected of
/host contents.
This commit is contained in:
Nikolay Amiantov 2019-05-12 09:35:12 +03:00
parent 7664ffbbaf
commit 06f27dc2e9
1 changed files with 23 additions and 6 deletions
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29
pkgs/build-support/build-fhs-userenv/chrootenv/chrootenv.c
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@ -18,7 +18,7 @@
if (expr) \
fail(#expr, errno);
const gchar *bind_blacklist[] = {"bin", "etc", "host", "usr", "lib", "lib64", "lib32", "sbin", NULL};
const gchar *bind_blacklist[] = {"bin", "etc", "host", "real-host", "usr", "lib", "lib64", "lib32", "sbin", NULL};
int pivot_root(const char *new_root, const char *put_old) {
return syscall(SYS_pivot_root, new_root, put_old);
@ -56,9 +56,12 @@ void bind_mount_item(const gchar *host, const gchar *guest, const gchar *name) {
void bind(const gchar *host, const gchar *guest) {
mount_tmpfs(guest);
pivot_host(guest);
g_autofree gchar *host_dir = g_build_filename("/host", host, NULL);
g_autoptr(GError) err = NULL;
g_autoptr(GDir) dir = g_dir_open(host, 0, &err);
g_autoptr(GDir) dir = g_dir_open(host_dir, 0, &err);
if (err != NULL)
fail("g_dir_open", errno);
@ -67,9 +70,7 @@ void bind(const gchar *host, const gchar *guest) {
while ((item = g_dir_read_name(dir)))
if (!g_strv_contains(bind_blacklist, item))
bind_mount_item(host, guest, item);
pivot_host(guest);
bind_mount_item(host_dir, "/", item);
}
void spit(const char *path, char *fmt, ...) {
@ -119,7 +120,23 @@ int main(gint argc, gchar **argv) {
spit("/proc/self/uid_map", "%d %d 1", uid, uid);
spit("/proc/self/gid_map", "%d %d 1", gid, gid);
bind("/", prefix);
// If there is a /host directory, assume this is nested chrootenv and use it as host instead.
gboolean nested_host = g_file_test("/host", G_FILE_TEST_EXISTS | G_FILE_TEST_IS_DIR);
g_autofree const gchar *host = nested_host ? "/host" : "/";
bind(host, prefix);
// Replace /host by an actual (inner) /host.
if (nested_host) {
fail_if(g_mkdir("/real-host", 0755));
fail_if(mount("/host/host", "/real-host", NULL, MS_BIND | MS_REC, NULL));
// For some reason umount("/host") returns EBUSY even immediately after
// pivot_root. We detach it at least to keep `/proc/mounts` from blowing
// up in nested cases.
fail_if(umount2("/host", MNT_DETACH));
fail_if(mount("/real-host", "/host", NULL, MS_MOVE, NULL));
fail_if(rmdir("/real-host"));
}
fail_if(chdir("/"));
fail_if(execvp(*argv, argv));