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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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1
PDP11/pdp11_rq.c
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@ -172,6 +172,7 @@ extern int32 MMR2;
#define unit_plug u4 /* drive unit plug value */ #define unit_plug u4 /* drive unit plug value */
#define io_status u5 /* io status from callback */ #define io_status u5 /* io status from callback */
#define io_complete u6 /* io completion flag */ #define io_complete u6 /* io completion flag */
/* we can re-use filebuf because we don't set UNIT_BUFABLE in flags */
#define rqxb filebuf /* xfer buffer */ #define rqxb filebuf /* xfer buffer */
#define RQ_RMV(u) ((drv_tab[GET_DTYPE (u->flags)].flgs & RQDF_RMV)? \ #define RQ_RMV(u) ((drv_tab[GET_DTYPE (u->flags)].flgs & RQDF_RMV)? \
UF_RMV: 0) UF_RMV: 0)

6
sim_disk.c
View file

@ -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_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); sim_disk_wrsect (uptr, 0, (uint8 *)uptr->filebuf, NULL, (cap + ctx->sector_size - 1) / ctx->sector_size);
} }
uptr->flags = uptr->flags & ~UNIT_BUF; if (uptr->flags & UNIT_MUSTBUF) { /* dyn alloc? */
}
free (uptr->filebuf); /* free buffers */ free (uptr->filebuf); /* free buffers */
uptr->filebuf = NULL; uptr->filebuf = NULL;
free (uptr->filebuf2); free (uptr->filebuf2);
uptr->filebuf2 = NULL; uptr->filebuf2 = NULL;
}
uptr->flags = uptr->flags & ~UNIT_BUF;
}
update_disk_footer (uptr); /* Update meta data if highwater has changed */ update_disk_footer (uptr); /* Update meta data if highwater has changed */