#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

int main(int argc, char *argv[])

{

int i;

/* TODO: this doesn't go anywhere useful right now. It would be nice to

* switch this to syslog() (or some other mechanism) so that we can

* actually read the contents.

*/

fprintf(stderr, "usermodehelper: ");

for (i = 0; i < argc; i++) {

fprintf(stderr, "%s ", argv[i]);

}

fprintf(stderr, "\n");

if (!strcmp(argv[0], "/sbin/mdev")) {

/* busybox uses /sbin/mdev for early uevent bootstrapping */

execv(argv[0], argv);

} else if (!strcmp(argv[0], "/sbin/modprobe")) {

/* allow modprobe */

execv(argv[0], argv);

} else if (!strcmp(argv[0], "/sbin/poweroff") ||

!strcmp(argv[0], "/sbin/reboot")) {

/* poweroff and reboot are allowed */

execv(argv[0], argv);

} else {

/* This means either we got an unexpected call from the kernel

* or someone is doing something nefarious. Some other possible

* expected callers are:

* - for core dumps. we don't have a "core" binary, and don't

* set this by default to anything. when we do, we need to

* whitelist it here

* - /linuxrc: we're not doing legacy root setup, so we don't

* need this

* - a few drivers and filesystems (drbd, nfs, nfsd, ocfs2)

* - cgroup notify_on_release handlers, which we do not set

* (but e.g. systemd needs, if anyone ever tries to boot

* that on linuxkit)

* - /sbin/request-key, which we don't provide

* - on x86, machine check

*

* Today we only call mdev and modprobe, but as we add more

* features to linuxkit this whitelist may need changing (or a

* policy, like always allow stuff in /sbin).

*/

exit(2);

}

perror("exec failed");

return 1;

}