kern/52338: fd(4) floppy disk driver & non-blocking I/O

[Yar Tikhiy]

>Number:         52338
>Category:       kern
>Synopsis:       fd(4) floppy disk driver & non-blocking I/O
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri May 16 09:50:14 PDT 2003
>Closed-Date:
>Last-Modified:
>Originator:     Yar Tikhiy
>Release:        FreeBSD 5.1-BETA i386
>Organization:
Moscow State University
>Environment:
System: FreeBSD stylish.chem.msu.su 5.1-BETA FreeBSD 5.1-BETA #1: Thu May 15 11:40:27 MSD 2003 yar at stylish.chem.msu.su:/usr/obj/usr/src/sys/STYLISH i386

>Description:

	If /dev/fdX has been opened in non-blocking mode, the
	inserted floppy type will never be autoselected.  So trying
	to get its parameters through DIOCGSECTORSIZE or DIOCGMEDIASIZE
	will cause panic on dereferencing the NULL fd->ft pointer.
	And reading from or writing to its descriptor will result
	in the ENXIO (Device not configured) error.

>How-To-Repeat:

	To see the panic, run the following test program on /dev/fd0:

	# ./fdtest /dev/fd0
	
=====================================================
	#include <sys/types.h>
	#include <sys/disk.h>
	#include <err.h>
	#include <fcntl.h>
	#include <stdio.h>
	#include <unistd.h>

	int
	main(int argc, char **argv)
	{
		int fd;
		unsigned blksz;
		off_t medsz;

		if (argc < 2)
			errx(2, "Args!");
		fd = open(argv[1], O_RDONLY | O_NDELAY);
		if (fd < 0)
			err(2, "open");
		if (ioctl(fd, DIOCGSECTORSIZE, &blksz) < 0)
			err(2, "DIOCGSECTORSIZE");
		if (ioctl(fd, DIOCGMEDIASIZE, &medsz) < 0)
			err(2, "DIOCGMEDIASIZE");
		printf("%u %lld\n", blksz, medsz);
		close(fd);
		return (0);
	}
=====================================================

	And the following program, written in somewhat poor style,
	will demonstrate the read(2) bug:

=====================================================
	#include <sys/types.h>
	#include <sys/disk.h>
	#include <err.h>
	#include <fcntl.h>
	#include <stdio.h>
	#include <unistd.h>

	int
	main(int argc, char **argv)
	{
		int fd;
		unsigned blksz;
		off_t medsz;
		char buf[512];

		if (argc < 2)
			errx(2, "Args!");
		fd = open(argv[1], O_RDONLY | O_NDELAY);
		if (fd < 0)
			err(2, "open");
		if (read(fd, buf, 512) < 512)
			err(2, "read");
		close(fd);
		return (0);
	}
=====================================================

>Fix:

	Not ready yet...
>Release-Note:
>Audit-Trail:
>Unformatted: