#define _GNU_SOURCE
#include <unistd.h>
+#include <signal.h>
#include "syscall.h"
+#include "libc.h"
+
+struct ctx {
+ size_t count;
+ const gid_t *list;
+ int ret;
+};
+
+static void do_setgroups(void *p)
+{
+ struct ctx *c = p;
+ if (c->ret<0) return;
+ int ret = __syscall(SYS_setgroups, c->count, c->list);
+ if (ret && !c->ret) {
+ /* If one thread fails to set groups after another has already
+ * succeeded, forcibly killing the process is the only safe
+ * thing to do. State is inconsistent and dangerous. Use
+ * SIGKILL because it is uncatchable. */
+ __block_all_sigs(0);
+ __syscall(SYS_kill, __syscall(SYS_getpid), SIGKILL);
+ }
+ c->ret = ret;
+}
int setgroups(size_t count, const gid_t list[])
{
- return syscall(SYS_setgroups, count, list);
+ /* ret is initially nonzero so that failure of the first thread does not
+ * trigger the safety kill above. */
+ struct ctx c = { .count = count, .list = list, .ret = 1 };
+ __synccall(do_setgroups, &c);
+ return __syscall_ret(c.ret);
}