I am not sure what the procedure for reporting bugs, but here
is a description of two bugs and a program that can can be used
to produce them.
$ uname -a
Linux fror.research.att.com 2.4.18-18.7.xsmp #1 SMP Wed Nov 13 19:01:42 EST 2002
The first problem is that files created with socketpair() are not accessible
via /dev/fd/n or /proc/$$/fd/n where n is the file descriptor returned
by socketpair(). Note that this is not a problem with pipe().
The second problem is that if fchmod(fd,S_IWUSR) is applied to the write end
of a pipe(), it causes the read() end to also be write only so that
opening /dev/fd/n for read fails.
The following program demonstrates these problems. If invoked without
arguments, socketpair() is used to create to files. Later the
open /dev/fd/n and /proc/$$/fd/n fail.
With one argument, pipe() is used instead of socketpair() and the
program works. With two arguments, pipe() is used bug fchmod()
is also called, and then it fails.
==================cut here======================
#include <sys/socket.h>
#include <sys/stat.h>
#include <stdio.h>
#include <errno.h>
int main(int argc, char *argv[])
{
char buff[256];
int pv[2], fd;
if(argc>1)
fd = pipe(pv);
else
fd = socketpair(PF_UNIX, SOCK_STREAM, 0, pv);
if(fd<0)
{
fprintf(stderr,"socketpar failed err=%d\n",errno);
exit(1);
}
if(argc<2)
{
if(shutdown(pv[0],1)< 0)
{
fprintf(stderr,"shutdown send failed err=%d\n",errno);
exit(1);
}
if(shutdown(pv[1],0)< 0)
{
fprintf(stderr,"shutdown recv failed err=%d\n",errno);
exit(1);
}
}
if(argc!=2)
{
fchmod(pv[0],S_IRUSR);
fchmod(pv[1],S_IWUSR);
}
sprintf(buff,"/dev/fd/%d\0",pv[0]);
errno = 0;
fd = open(buff,0);
fprintf(stderr,"name=%s fd=%d errno=%d\n",buff,fd,errno);
sprintf(buff,"/proc/%d/fd/%d\0",getpid(),pv[0]);
fd = open(buff,0);
fprintf(stderr,"name=%s fd=%d errno=%d\n",buff,fd,errno);
return(0);
}
==================cut here======================
David Korn
dgk@research.att.com
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This archive was generated by hypermail 2b29 : Wed Jul 23 2003 - 22:00:49 EST