Bug 154405 - mkswap should clear key parts of the block device
mkswap should clear key parts of the block device
Product: Fedora
Classification: Fedora
Component: util-linux (Show other bugs)
All Linux
medium Severity medium
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Assigned To: Karel Zak
Ben Levenson
Depends On:
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Reported: 2005-04-11 11:08 EDT by David Zeuthen
Modified: 2013-03-05 22:43 EST (History)
1 user (show)

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Fixed In Version:
Doc Type: Bug Fix
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Last Closed: 2005-10-17 11:46:27 EDT
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Description David Zeuthen 2005-04-11 11:08:36 EDT
Description of problem:

The first 512 bytes of a block device formatted with mkswap are not cleared;
this means that filesystems probers may errornously detect a swap partition as a
vfat partition, mount it and then data corruption may happen.

Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:

Kay Sievers <kay.sievers@vrfy.org> made a test program that creates a loop
device and formats, cross-formats and probes it with volume_id if the fs is
recognized. For now only: swap, fat, ext2, ext3 are cross-tested and it finds
only one error. 

1. Download http://people.redhat.com/davidz/vid-044.tar.gz
2. Unpack archive
3. make
4. as root run ./fs-label-cross-test.pl from with the vid directory of the archive
Actual results:

mkswap should clear parts of the block device where other OS'es expects to find
file system signatures. For most practical situations this is clearing at least
the first 2048 bytes.

Expected results:

Additional info:
Comment 3 Karel Zak 2005-09-30 11:56:28 EDT
BTW, there's libblkid (from e2fsprogs package) that does same work as the "vid"
code. The best solution will be use same code in all our packages rather than
duplicate funcionality. The libblkid is really good designed and doesn't have a
problem with swap detection :-)
Comment 4 Karel Zak 2005-10-17 11:46:27 EDT
That's feature that mkswap doesn't touch the first block of swap area.

man mkswap:

The new style header does not touch the first block, so may be preferable, in
case you have a boot loader or disk label there.

Sorry. CLOSING...

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