> Hello, i have found this bug in (z)ftape under Linux-2.2.5,
> i hope the attached Files provide Enough information,
> if they do not, let me know (fhopge@cin.net)
> thank you.
[describes how "mt tell" causes oops]
Yep, I can reproduce this bug.
Insert a tape, mt rewind, mt tell --> oops. This is bad
since is leaves the ftape driver in a "busy" state and
it even seems to leave the hardware (a Seagate TST3200R
on a CTC-2Mb fast controller in my case) in a useless state;
I have to power-cycle to get it back.
The problem appears to be that the driver isn't properly
initialized at this point: in particular the volume table
doesn't seem to have been read. First mt_tell() called
zft_find_volume() with zft_pos.seg_pos == -1: this -1
is promptly cast to unsigned which caused the first "<"
comparison in zft_find_volume() to fail. Second, "cur_vtbl"
is NULL, which caused the NULL ptr oops.
The proper fix would be ensure that the volume table has been
read at this point, but I don't really know where and how
this should be done. The patch below is a bandaid which cures
the immediate problem for me.
(ftape-4.02 has fixed this bug. I have a big patch which adds
ftape-4.02 to kernel 2.2.5 and fixes some bugs; contact me
if you want it.)
/ Mikael
--- linux-2.2.5-ac6/drivers/char/ftape/zftape/zftape-vtbl.c.~1~ Tue Nov 25 23:45:28 1997
+++ linux-2.2.5-ac6/drivers/char/ftape/zftape/zftape-vtbl.c Thu Apr 8 23:01:04 1999
@@ -720,7 +720,7 @@
tape_vtbl.blk_sz = zft_blk_sz;
TRACE_EXIT &tape_vtbl;
}
- if (seg_pos < zft_first_vtbl->start_seg) {
+ if ((int)seg_pos < (int)zft_first_vtbl->start_seg) {
TRACE_EXIT (cur_vtbl = zft_first_vtbl);
}
while (seg_pos > cur_vtbl->end_seg) {
--- linux-2.2.5-ac6/drivers/char/ftape/zftape/zftape-ctl.c.~1~ Mon May 11 19:50:15 1998
+++ linux-2.2.5-ac6/drivers/char/ftape/zftape/zftape-ctl.c Thu Apr 8 22:59:35 1999
@@ -552,10 +552,14 @@
*/
static int mt_tell(int *arg)
{
+ const zft_volinfo *vtbl;
TRACE_FUN(ft_t_flow);
- *arg = zft_div_blksz(zft_pos.volume_pos,
- zft_find_volume(zft_pos.seg_pos)->blk_sz);
+ vtbl = zft_find_volume(zft_pos.seg_pos);
+ *arg = vtbl->blk_sz
+ ? zft_div_blksz(zft_pos.volume_pos, vtbl->blk_sz)
+ : -1;
+
TRACE_EXIT 0;
}
-
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