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sim_disk.c: only free filebuf if it was allocated here too.

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PDP11/pdp11_rq.c re-uses ->filebuf as a sector buffer (under the #defined
name rqxb) and allocates it as such. If an RQ disk is detached and
another attached, this buffer would be lost and the pointer reset to
NULL. sim_disk.c would only allocate the buffer if UNIT_BUFABLE is set,
which means to buffer the whole disk. Since this rightly isn't set on RQ
disks, the pointer would remain NULL and segfaults would ensue.  See
open-simh issue 274.
add comment about safe re-use of filebuf
This commit is contained in:
Olaf Seibert
2023-07-15 15:47:39 +02:00
committed by Paul Koning
parent 1e371e7c98
commit 86ffe4bec2
2 changed files with 7 additions and 4 deletions
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10
sim_disk.c
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@@ -3380,12 +3380,14 @@ if ((uptr->flags & UNIT_BUF) && (uptr->filebuf)) {
sim_messagef (SCPE_OK, "%s: writing buffer to file: %s\n", sim_uname (uptr), uptr->filename);
sim_disk_wrsect (uptr, 0, (uint8 *)uptr->filebuf, NULL, (cap + ctx->sector_size - 1) / ctx->sector_size);
}
if (uptr->flags & UNIT_MUSTBUF) { /* dyn alloc? */
free (uptr->filebuf); /* free buffers */
uptr->filebuf = NULL;
free (uptr->filebuf2);
uptr->filebuf2 = NULL;
}
uptr->flags = uptr->flags & ~UNIT_BUF;
}
free (uptr->filebuf); /* free buffers */
uptr->filebuf = NULL;
free (uptr->filebuf2);
uptr->filebuf2 = NULL;
update_disk_footer (uptr); /* Update meta data if highwater has changed */