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Date:      Tue, 26 Nov 1996 23:05:10 +1100
From:      Bruce Evans <bde@zeta.org.au>
To:        jkh@time.cdrom.com, rnordier@iafrica.com
Cc:        grog@lemis.de, hackers@FreeBSD.ORG
Subject:   Re: A simple way to crash your system.
Message-ID:  <199611261205.XAA06641@godzilla.zeta.org.au>

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>FWIW, the table below represents a couple of months of collecting
>data from users on -questions, who reported that the msdosfs had
>seriously corrupted a UFS partition.
>
>       DRIVE              DOS START        DOS END
>       cyl  head sect ||  cyl  head sect   cyl  head sect      size
>-------------------------------------------------------------------
>wd0 |  525 | 64 |  63 ||    0 |  1 |  1 |  126 | 63 |  63 |  512001
>wd0 | 2099 | 64 |  63 ||    0 |  1 |  1 |  189 | 63 |  63 |  766017
>      same drive      ||  250 |  0 |  1 |  523 | 63 |  63 | 1104768
>wd0 |  788 | 64 |  63 ||    0 |  1 |  1 |  787 | 63 |  63 | 3177153
>wd0 |  621 | 64 |  63 ||    0 |  1 |  1 |  619 | 63 |  63 | 2499777
>wd0 |  525 | 64 |  63 ||    0 |  1 |  1 |  523 | 63 |  63 | 2112705
>
>*All* problems occurred with the DOS FS on a 64/63 IDE drive.  FIPS
>was not necessarily used.  In one case, the corrupted UFS fs was
>actually on another drive.

That can't be the problem, since FreeBSD ignores the geometry in both
the driver and in msdosfs.

>Unless someone is aware of the problem being more general, it may

MAXBSIZE = 16384.  I'm not sure exactly what using larger blocks breaks,
if anything (blocks up to MAXPHYS=64K are sometimes used and work OK),
but ufs is careful to reject file systems with a larger block size.

Bruce



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