[Bug 1831] Incorrect label/uuid may be returned for swap partitions

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=1831

--- Comment #1 from Denys Vlasenko <vda.linux at googlemail.com>  ---
Well, if image does contain both vfat and swapspace signatures,
volume_id_probe_all() inevitably will get confused. Why do you think swapspace
signature should get preference?


Isn't it admin's error to not clear swapspace before mkswap'ing it?


Let's see whether "standard" mkswap clears 1st page:

Here is 16 Mb image which was filled with 0a bytes and them "mkswap"ed by
util-linux-ng 2.17.2:

00000000  0a 0a 0a 0a 0a 0a 0a 0a  0a 0a 0a 0a 0a 0a 0a 0a  |................|
*
00000400  01 00 00 00 ff 0f 00 00  00 00 00 00 d8 74 24 f8  |.............t$.|
00000410  41 56 47 d1 b3 59 97 fa  e9 64 f6 33 00 00 00 00  |AVG..Y...d.3....|
00000420  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000ff0  00 00 00 00 00 00 53 57  41 50 53 50 41 43 45 32  |......SWAPSPACE2|
00001000  0a 0a 0a 0a 0a 0a 0a 0a  0a 0a 0a 0a 0a 0a 0a 0a  |................|
*
01000000

And the same test with busybox:

00000000  0a 0a 0a 0a 0a 0a 0a 0a  0a 0a 0a 0a 0a 0a 0a 0a  |................|
*
00000400  01 00 00 00 ff 0f 00 00  00 00 00 00 32 43 bd 3d  |............2C.=|
00000410  79 d5 49 51 af 45 d2 11  b6 6b dd f2 00 00 00 00  |y.IQ.E...k......|
00000420  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000600  00 00 00 00 0a 0a 0a 0a  0a 0a 0a 0a 0a 0a 0a 0a  |................|
00000610  0a 0a 0a 0a 0a 0a 0a 0a  0a 0a 0a 0a 0a 0a 0a 0a  |................|
*
00000ff0  0a 0a 0a 0a 0a 0a 53 57  41 50 53 50 41 43 45 32  |......SWAPSPACE2|
00001000  0a 0a 0a 0a 0a 0a 0a 0a  0a 0a 0a 0a 0a 0a 0a 0a  |................|
*
01000000

That is, 1st page was not erased in both cases.

util-linux-ng 2.17.2 claims to erase it when it does not see any partition
tables and is not run in whole disk (that is, is it works on /dev/XdYNN, not on
/dev/XdY), or with -f flag.

We can add -f flag, but then many users will forget to use it...

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