Re: lib/44807: something broken in stat(2)

[christos%zoulas.com@localhost (Christos Zoulas)]

On Mar 30,  6:15pm, jruohonen%iki.fi@localhost (Jukka Ruohonen) wrote:
-- Subject: lib/44807: something broken in stat(2)

| >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.

It works as expected. /dev/bpf is a cloner, so you get a new instance each
time you run. The instance does not have a place in the filesystem, so you
get the "right" information as far as that is concerned.

$ ./a.out
dev=[23, 12761] # major 23 always
mode=0  # correct
ino=0   # correct
nlink=0 # correct
uid=0   # correct
gid=0   # correct
rdev=[0, 0]     # irrelevant
a=[1301510133, 111864879] Wed Mar 30 14:35:33 2011 # correct times
m=[1301510133, 111864879] Wed Mar 30 14:35:33 2011 # correct times
c=[1301510133, 111864879] Wed Mar 30 14:35:33 2011 # correct times
birth=[1301510133, 111864879] Wed Mar 30 14:35:33 2011 # correct times
size=0  # correct
blocks=0        # correct
blksize=0       # correct
flags=0 # correct
gen=0   # correct

Now fchown on the fd does not work, so :-)


christos

----

#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <time.h>
#include <string.h>
#include <fcntl.h>
#include <stdlib.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);
        (void)close(fd);

        if (rv < 0)
                return EXIT_FAILURE;

#define PR(t,f) printf(#f "=%ll" #t "\n", \
    (long long)st.st_ ## f)
#define PRT(f)  printf(#f "=[%llu, %llu] %s", \
    (long long)st.st_ ## f ## timespec.tv_sec, \
    (long long)st.st_ ## f ## timespec.tv_nsec, \
    ctime(&st.st_ ## f ## timespec.tv_sec))
#define PRD(f)  printf(#f "=[%llu, %llu]\n", \
    (long long)major(st.st_ ## f), \
    (long long)minor(st.st_ ## f))

        PRD(dev);
        PR(o,mode);
        PR(d,ino);
        PR(d,nlink);
        PR(u,uid);
        PR(u,gid);
        PRD(rdev);
        PRT(a);
        PRT(m);
        PRT(c);
        PRT(birth);
        PR(u,size);
        PR(u,blocks);
        PR(u,blksize);
        PR(x,flags);
        PR(u,gen);

        return EXIT_SUCCESS;
}