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a4e0a594b1
The binary is used in tandem with CONFIG_STATIC_USERMODEHELPER=y in 4.11+, see the big comment in the binary for the current whitelist of binaries. Signed-off-by: Tycho Andersen <tycho@docker.com>
56 lines
1.7 KiB
C
56 lines
1.7 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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int main(int argc, char *argv[])
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{
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int i;
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/* TODO: this doesn't go anywhere useful right now. It would be nice to
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* switch this to syslog() (or some other mechanism) so that we can
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* actually read the contents.
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*/
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fprintf(stderr, "usermodehelper: ");
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for (i = 0; i < argc; i++) {
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fprintf(stderr, "%s ", argv[i]);
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}
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fprintf(stderr, "\n");
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if (!strcmp(argv[0], "/sbin/mdev")) {
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/* busybox uses /sbin/mdev for early uevent bootstrapping */
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execv(argv[0], argv);
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} else if (!strcmp(argv[0], "/sbin/modprobe")) {
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/* allow modprobe */
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execv(argv[0], argv);
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} else if (!strcmp(argv[0], "/sbin/poweroff") ||
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!strcmp(argv[0], "/sbin/reboot")) {
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/* poweroff and reboot are allowed */
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execv(argv[0], argv);
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} else {
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/* This means either we got an unexpected call from the kernel
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* or someone is doing something nefarious. Some other possible
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* expected callers are:
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* - for core dumps. we don't have a "core" binary, and don't
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* set this by default to anything. when we do, we need to
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* whitelist it here
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* - /linuxrc: we're not doing legacy root setup, so we don't
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* need this
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* - a few drivers and filesystems (drbd, nfs, nfsd, ocfs2)
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* - cgroup notify_on_release handlers, which we do not set
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* (but e.g. systemd needs, if anyone ever tries to boot
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* that on linuxkit)
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* - /sbin/request-key, which we don't provide
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* - on x86, machine check
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*
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* Today we only call mdev and modprobe, but as we add more
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* features to linuxkit this whitelist may need changing (or a
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* policy, like always allow stuff in /sbin).
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*/
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exit(2);
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}
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perror("exec failed");
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return 1;
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}
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