[Freemint-discuss] Bug report and patch

[Roger B. <an...@xp...>]

The attached patch fixes a bug in the TOSONLY code in usb_storage.c.  It does 
not affect FreeMiNT, but it does affect the STORAGE.PRG that is used in support 
of USB sticks on plain TOS (and EmuTOS), and the code is in the FreeMiNT 
sources, so I am submitting the patch here.

Problem description:
During STORAGE.PRG startup, if the current max_sect_siz in the AHDI structure 
is not the same as the maximum logical sector size obtained from XHDI, the 
program installs a new AHDI structure and a new set of cache buffers.  It then 
copies the data from the old buffers to the new ones.  However, it only copies 
the first 512 bytes of each buffer; the rest of the buffer was zeroed after 
being malloc'ed and remains that way.

As a result, if max_sect_siz is not the same as the XHDI size, and max_sect_siz 
is greater than 512, the in-memory copy of sectors will be corrupt after 
STORAGE.PRG has run.  If the cached sectors are from directories, then files or 
folders will temporarily disappear; if those sectors are subsequently written 
to, the bad data will be flushed to disk, causing filesystem corruption.

Fix:
The fix merely sets the copy length correctly.

Roger Burrows