libc-top-half/musl/src/unistd/setxid.c

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