kernel-ark/drivers/scsi/sr.h
Pete Zaitcev 51490c89f9 [SCSI] sr.c: Fix getting wrong size
Here's the problem. Try to do this on 2.6.12:
- Kill udev and HAL
- Insert a CD-ROM into a SCSI or USB CD-ROM drive
- Run dd if=/dev/scd0
- cat /sys/block/sr0/size
- Eject the CD, insert a different one
- Run dd if=/dev/scd0
This is likely to do "access beyond the end of device", if you let it
- cat /sys/block/sr0/size
This shows the size of a previous CD, even though dd was supposed
to revalidate the device.
- Run dd if=/dev/scd0
The second run of dd works correctly!

The bug was introduced in 2.5.31, when Al fixes the recursive opens
in partitioning. Before, the code worked like this:
- Block layer called cdrom_open directly
- cdrom_open called sr_open
- sr_open called check_disk_change
- check_disk_change called sr_media_change
- sr_media_change did cd->needs_disk_change=1
- before returning sr_open tested cd->needs_disk_change
  and called get_sector_size.

In 2.6.12, the check_disk_change is called from cdrom_open only. Thus:
- Block layer calls sr_bd_open
- sr_bd_open calls cdrom_open
- cdrom_open calls sr_open
- sr_open tests cd->needs_disk_change, which wasn't set yet; returns
- cdrom_open calls check_disk_change
- check_disk_change calls sr_media_change
- sr_media_change does cd->needs_disk_change=1, but nobody cares

Acked by: Alexander Viro <aviro@redhat.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
2005-08-28 11:14:12 -05:00

68 lines
2.2 KiB
C

/*
* sr.h by David Giller
* CD-ROM disk driver header file
*
* adapted from:
* sd.h Copyright (C) 1992 Drew Eckhardt
* SCSI disk driver header file by
* Drew Eckhardt
*
* <drew@colorado.edu>
*
* Modified by Eric Youngdale eric@andante.org to
* add scatter-gather, multiple outstanding request, and other
* enhancements.
*/
#ifndef _SR_H
#define _SR_H
#include <linux/genhd.h>
#include <linux/kref.h>
struct scsi_device;
/* The CDROM is fairly slow, so we need a little extra time */
/* In fact, it is very slow if it has to spin up first */
#define IOCTL_TIMEOUT 30*HZ
typedef struct scsi_cd {
struct scsi_driver *driver;
unsigned capacity; /* size in blocks */
struct scsi_device *device;
unsigned int vendor; /* vendor code, see sr_vendor.c */
unsigned long ms_offset; /* for reading multisession-CD's */
unsigned use:1; /* is this device still supportable */
unsigned xa_flag:1; /* CD has XA sectors ? */
unsigned readcd_known:1; /* drive supports READ_CD (0xbe) */
unsigned readcd_cdda:1; /* reading audio data using READ_CD */
struct cdrom_device_info cdi;
/* We hold gendisk and scsi_device references on probe and use
* the refs on this kref to decide when to release them */
struct kref kref;
struct gendisk *disk;
} Scsi_CD;
int sr_do_ioctl(Scsi_CD *, struct packet_command *);
int sr_lock_door(struct cdrom_device_info *, int);
int sr_tray_move(struct cdrom_device_info *, int);
int sr_drive_status(struct cdrom_device_info *, int);
int sr_disk_status(struct cdrom_device_info *);
int sr_get_last_session(struct cdrom_device_info *, struct cdrom_multisession *);
int sr_get_mcn(struct cdrom_device_info *, struct cdrom_mcn *);
int sr_reset(struct cdrom_device_info *);
int sr_select_speed(struct cdrom_device_info *cdi, int speed);
int sr_audio_ioctl(struct cdrom_device_info *, unsigned int, void *);
int sr_dev_ioctl(struct cdrom_device_info *, unsigned int, unsigned long);
int sr_is_xa(Scsi_CD *);
/* sr_vendor.c */
void sr_vendor_init(Scsi_CD *);
int sr_cd_check(struct cdrom_device_info *);
int sr_set_blocklength(Scsi_CD *, int blocklength);
#endif