Re: [Libevent-users] Unitialized Memory Read when pushing >64 events at once

[Nick Mathewson <nickm@xxxxxxxxxxxxx>]

On Sun, May 29, 2011 at 9:25 PM, Nick Mathewson <nickm@xxxxxxxxxxxxx> wrote:
[...]
> Below is a short program I tried to use to reproduce this, but
> valgrind didn't tell me about any reads of uninitialized memory.  Does
> purify complain about the program below?
>

And here's a simpler program to check whether purify has the false
positive that I suspect it might.

If purify complains about this code using uninitialized RAM, I believe
purify is wrong, or my understanding of epoll is somehow deficient.
If purify doesn't complain about this code, then we are likely to have
a genuine libevent bug on our hands.

=====
#include <string.h>
#include <stdio.h>
#include <sys/epoll.h>
#include <sys/socket.h>

int main(int c, char **v)
{
   int epfd;
   int fd[128];
   int i;

   epfd = epoll_create(1000);

   for (i=0;i<128;++i) {
     struct epoll_event ctl;
     fd[i] = socket(AF_INET, SOCK_DGRAM, 0);
     if (fd[i]<0) {
       perror("socket");
       return 1;
     }
     memset(&ctl, 0, sizeof(ctl));
     ctl.data.fd = fd[i];
     ctl.events = EPOLLOUT;
     if (epoll_ctl(epfd, EPOLL_CTL_ADD, fd[i], &ctl) < 0) {
       perror("epoll_ctl");
       return 1;
     }
   }

   for (i = 0; i < 10; ++i) {
     int j, res;
     struct epoll_event events[200];
     res = epoll_wait(epfd, events, 200, 0);
     printf("%d\n", res);
     if (res < 0) break;
     for (j=0;j<res;++j) {
        printf("  - %d\n", events[j].data.fd);
     }
   }

   return 0;
}
=====

hth,
-- 
Nick
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