Date: Tue, 30 Aug 2005 14:31:35 GMT From: Lev Levinson <llevinson@inbox.ru> To: freebsd-gnats-submit@FreeBSD.org Subject: misc/85481: reading from fd0 when floppy disk is write-protected Message-ID: <200508301431.j7UEVZBi031335@www.freebsd.org> Resent-Message-ID: <200508301440.j7UEeIZR045591@freefall.freebsd.org>
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>Number: 85481
>Category: misc
>Synopsis: reading from fd0 when floppy disk is write-protected
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Tue Aug 30 14:40:18 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator: Lev Levinson
>Release: 5.4-RELEASE
>Organization:
>Environment:
FreeBSD 5.4-RELEASE FreeBSD 5.4-RELEASE #0: Sun May 8 10:21:06 UTC 2005 root@harlow.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC i386
>Description:
Reading n x 512 byte blocks from /dev/fd0 result in "Input/output error" when n IS NOT DIVISOR of 36 and floppy disk is write-protected.
for example,
dd if=/dev/fd0 of=/dev/null bs=512
dd if=/dev/fd0 of=/dev/null bs=1024 # 2x512
dd if=/dev/fd0 of=/dev/null bs=1536 # 3x512
dd if=/dev/fd0 of=/dev/null bs=2048 # 4x512
dd if=/dev/fd0 of=/dev/null bs=3072 # 6x512
dd if=/dev/fd0 of=/dev/null bs=4608 # 9x512
works well, but
dd if=/dev/fd0 of=/dev/null bs=2560 # 5x512
dd if=/dev/fd0 of=/dev/null bs=3584 # 7x512
dd if=/dev/fd0 of=/dev/null bs=4096 # 8x512
dd if=/dev/fd0 of=/dev/null bs=5120 # 10x512
reports input-output error.
tar reads file with 20 x 512 byte blocks, and
tar -xzf /dev/fd0
no works if disk is write-protected.
but
tar -xzf /dev/fd0 -b 36
works.
>How-To-Repeat:
1 Boot and login as root
2 Insert write protected floppy disk.
3 dd if=/dev/fd0 of=/dev/null bs=4096
(or bs = n x 512, where n is not divisor of 36 - number of sectors per floppy track)
>Fix:
In function fdc_worker (src/sys/dev/fdc/fdc.c:746) i found this line:
if (bp != NULL &&
(fdc->retry >= retries || (fd->flags & FDOPT_NORETRY))) {
In this line, option (BUT NOT FLAG!!!) FDOPT_NORETRY AND-ed against
field fd->flags (BUT NOT fd->options).
Option FDOPT_NORETRY has same value as a flag FD_WP (write protected). Thus, instead "need more reads" we have "Disk is write-protected" in condition.
For fix this bug, code mast be like this:
if (bp != NULL &&
(fdc->retry >= retries || (fd->options & FDOPT_NORETRY))) {
>Release-Note:
>Audit-Trail:
>Unformatted:
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