1#define _GNU_SOURCE
 2#include <unistd.h>
 3#include <signal.h>
 4#include "syscall.h"
 5#include "libc.h"
 6
 7struct ctx {
 8	size_t count;
 9	const gid_t *list;
10	int ret;
11};
12
13static void do_setgroups(void *p)
14{
15	struct ctx *c = p;
16	if (c->ret<0) return;
17	int ret = __syscall(SYS_setgroups, c->count, c->list);
18	if (ret && !c->ret) {
19		/* If one thread fails to set groups after another has already
20		 * succeeded, forcibly killing the process is the only safe
21		 * thing to do. State is inconsistent and dangerous. Use
22		 * SIGKILL because it is uncatchable. */
23		__block_all_sigs(0);
24		__syscall(SYS_kill, __syscall(SYS_getpid), SIGKILL);
25	}
26	c->ret = ret;
27}
28
29int setgroups(size_t count, const gid_t list[])
30{
31	/* ret is initially nonzero so that failure of the first thread does not
32	 * trigger the safety kill above. */
33	struct ctx c = { .count = count, .list = list, .ret = 1 };
34	__synccall(do_setgroups, &c);
35	return __syscall_ret(c.ret);
36}