Date: Sat, 17 May 2003 00:20:14 -0700 (PDT) From: Bruce Evans <bde@zeta.org.au> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/52338: fd(4) floppy disk driver & non-blocking I/O Message-ID: <200305170720.h4H7KELq047382@freefall.freebsd.org>
next in thread | raw e-mail | index | archive | help
The following reply was made to PR kern/52338; it has been noted by GNATS.
From: Bruce Evans <bde@zeta.org.au>
To: Yar Tikhiy <yar@comp.chem.msu.su>
Cc: FreeBSD-gnats-submit@freebsd.org, freebsd-bugs@freebsd.org
Subject: Re: kern/52338: fd(4) floppy disk driver & non-blocking I/O
Date: Sat, 17 May 2003 17:18:57 +1000 (EST)
On Fri, 16 May 2003, Yar Tikhiy wrote:
> >Description:
>
> If /dev/fdX has been opened in non-blocking mode, the
> inserted floppy type will never be autoselected. So trying
> to get its parameters through DIOCGSECTORSIZE or DIOCGMEDIASIZE
> will cause panic on dereferencing the NULL fd->ft pointer.
> And reading from or writing to its descriptor will result
> in the ENXIO (Device not configured) error.
I made the obvious quick for for the null pointer panics when they were
implemented:
%%%
Index: fd.c
===================================================================
RCS file: /home/ncvs/src/sys/isa/fd.c,v
retrieving revision 1.244
diff -u -2 -r1.244 fd.c
--- fd.c 11 Jan 2003 20:10:41 -0000 1.244
+++ fd.c 11 Jan 2003 21:02:32 -0000
@@ -2623,12 +2788,22 @@
* FD_NONBLOCK still being set.
*/
- switch (cmd) {
+#ifdef TEST_LABELLING
+ /* XXX only some slice ioctls are non-blocking. */
+ error = dsioctl(dev, cmd, addr, flag, &fd->slices);
+ if (error != ENOIOCTL)
+ return (error);
+#endif
+ switch (cmd) {
case DIOCGMEDIASIZE:
- *(off_t *)addr = (128 << (fd->ft->secsize)) * fd->ft->size;
+ if (fd->ft == 0)
+ return (ENXIO);
+ *(off_t *)addr = (128 << fd->ft->secsize) * fd->ft->size;
return (0);
case DIOCGSECTORSIZE:
- *(u_int *)addr = 128 << (fd->ft->secsize);
+ if (fd->ft == 0)
+ return (ENXIO);
+ *(u_int *)addr = 128 << fd->ft->secsize;
return (0);
%%%
Other changes in this patch:
- local code (TEST_LABELLING).
- fix 2 style bugs (excessive parentheses).
Style bugs in this patch:
- '0' is used for a null pointer constant to give bug for bug compatibility
with other checks for fd->ft being a null pointer.
Not autoselecting for the O_NONBLOCK case seems to be a feature.
Autoselecting requires even more blocking than does starting the motor,
and it would be just bogus to autoselect for an open whose purpose is
to set the type.
fd->ft may be NULL for other reasons, so the null pointer checks are
needed no matter how O_NONBLOCK is handled.
Bruce
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200305170720.h4H7KELq047382>