1#include <unistd.h>
2#include <errno.h>
3#include "syscall.h"
4#include "libc.h"
5#include "pthread_impl.h"
6
7struct ctx {
8	int id, eid, sid;
9	int nr, err;
10};
11
12static void do_setxid(void *p)
13{
14	struct ctx *c = p;
15	if (c->err>0) return;
16	int ret = -__syscall(c->nr, c->id, c->eid, c->sid);
17	if (ret && !c->err) {
18		/* If one thread fails to set ids after another has already
19		 * succeeded, forcibly killing the process is the only safe
20		 * thing to do. State is inconsistent and dangerous. Use
21		 * SIGKILL because it is uncatchable. */
22		__block_all_sigs(0);
23		__syscall(SYS_kill, __syscall(SYS_getpid), SIGKILL);
24	}
25	c->err = ret;
26}
27
28int __setxid(int nr, int id, int eid, int sid)
29{
30	/* err is initially nonzero so that failure of the first thread does not
31	 * trigger the safety kill above. */
32	struct ctx c = { .nr = nr, .id = id, .eid = eid, .sid = sid, .err = -1 };
33	__synccall(do_setxid, &c);
34	if (c.err) {
35		if (c.err>0) errno = c.err;
36		return -1;
37	}
38	return 0;
39}
40