volume_id: off by one error detecting FAT16 vs FAT32

Denys Vlasenko vda.linux at googlemail.com
Fri Mar 15 08:58:19 UTC 2019


Applied, thanks!

On Thu, Mar 14, 2019 at 5:38 PM Thomas Frauendorfer
<thomas.frauendorfer at gmail.com> wrote:
>
> Hello,
>
> Busybox detects a FAT file system with 65524 clusters as FAT32 while
> it should handle it as FAT16. Because of that blkid cannot detect the
> uuid or label on a FAT with 65524 clusters.
>
> The attached patch fixes that mistake.
>
> The cluster count values are defined in:
> Microsoft Extensible Firmware Initiative
> FAT32 File System Specification
> FAT: General Overview of On-Disk Format
>
> I used version 1.03 from December 6,2000
>
> The cluster count values are defined in pages 14 and 15 of that specification.
>
> Most users will probably not encounter that bug because the
> specification also states that file system creation code should stay
> away at least 16 clusters from that cluster count to avoid bugs in
> incorrect FAT code.
>
> Kind regards,
> Thomas
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