lib/44807: something broken in stat(2)

[Jukka Ruohonen <jruohonen%iki.fi@localhost>]

>Number:         44807
>Category:       lib
>Synopsis:       something broken in stat(2)
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    lib-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Mar 30 18:15:00 +0000 2011
>Originator:     Jukka Ruohonen
>Release:        5.1 - 5.99.48
>Organization:
-
>Description:

Another one caught by automated tests.

Something related to stat(2) is seriously broken somewhere. For instance,
opening "/dev/bpf" and stat'ing it either fails or reports odd results.

While I haven't done any analysis, it seems that this might be related to
the old, closed, bugs:

        PR kern/37550: fstat(1) not reporting open descriptors properly
        PR kern/37878: fdclone(9) suspected of not working well with fstat(1)

Given that those were fixed, it seems that this is again a regression.

>How-To-Repeat:

To add more weirdness, the following program prints a value 0 on 5.99.48,
but the fstat(2) fails on 5.1.

#include <sys/stat.h>

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

int
main(void)
{
        struct stat st;
        int fd, rv;

        (void)memset(&st, 0, sizeof(struct stat));

        fd = open("/dev/bpf", O_RDONLY);

        if (fd < 0)
                return EXIT_FAILURE;

        rv = fstat(fd, &st);

        if (rv < 0)
                return EXIT_FAILURE;

        (void)printf("mode = %u\n", st.st_mode);
        (void)close(fd);

        return EXIT_SUCCESS;
}

>Fix:

Unknown.