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#include <unistd.h>
#include <signal.h>
#include "syscall.h"
#include "libc.h"
struct ctx {
int id, eid, sid;
int nr, ret;
};
static void do_setxid(void *p)
{
struct ctx *c = p;
if (c->ret<0) return;
int ret = __syscall(c->nr, c->id, c->eid, c->sid);
if (ret && !c->ret) {
/* If one thread fails to set ids 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 __setxid(int nr, int id, int eid, int sid)
{
/* ret is initially nonzero so that failure of the first thread does not
* trigger the safety kill above. */
struct ctx c = { .nr = nr, .id = id, .eid = eid, .sid = sid, .ret = 1 };
__synccall(do_setxid, &c);
return __syscall_ret(c.ret > 0 ? -EAGAIN : c.ret);
}
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