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1 #define _GNU_SOURCE
2 #include <unistd.h>
3 #include <signal.h>
4 #include "syscall.h"
5 #include "libc.h"
6 
7 struct ctx {
8 	size_t count;
9 	const gid_t *list;
10 	int ret;
11 };
12 
do_setgroups(void * p)13 static 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 
setgroups(size_t count,const gid_t list[])29 int 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 }
37