src/linux/setgroups.c

   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
  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
  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 }