On Tue, Mar 27, 2018 at 07:50:18PM +0200, Otto Moerbeek wrote:
> On Tue, Mar 27, 2018 at 12:46:03PM +0200, Tobias Stoeckmann wrote:
>
> > Resending this old diff. Adjusted to apply with -current source:
> >
> > Illegal fragmentation block sizes can trigger division by zero in the
> > disklabel and fsck_ffs tools.
> >
> > See this sequence of commands to reproduce:
> >
> > # dd if=/dev/zero of=nofrag.iso bs=1M count=1
> > # vnconfig vnd0 nofrag.iso
> > # disklabel -e vnd0
> >
> > Create 'a' and set fsize = bsize = 1. A line like this one will do
> > a: 2048 0 4.2BSD 1 1 1
> >
> > # fsck_ffs vnd0a
> > ** /dev/vnd0a (vnd0a)
> > BAD SUPER BLOCK: MAGIC NUMBER WRONG
> > Floating point exception (core dumped)
> > # disklabel -E vnd0
> > Label editor (enter '?' for help at any prompt)
> > > m a
> > offset: [0]
> > size: [2048]
> > FS type: [4.2BSD]
> > Floating point exception (core dumped)
> > # vnconfig -u vnd0
Hmm, on what platform are you doing this? I could not reproduce your
problem on arm64 -current,
-Otto
> >
> > A fragmentation (block) size smaller than a sector size is not valid
> > while using "disklabel -E", and really doesn't make sense. While
> > using "disklabel -e", not all validation checks are performed, which
> > makes it possible to enter invalid values.
> >
> > If "disklabel -E" is used without the expert mode, fragmentation sizes
> > cannot be changed and will be just accepted from the parsed disklabel,
> > resulting in a division by zero if they are too small.
> >
> > And the same happens in fsck_ffs. Instead of coming up with a guessed
> > value in fsck_ffs, I think it's better to simply fail and let the user
> > fix the disklabel. After all, it shouldn't be fsck_ffs's duty to fix
> > faulty values outside the filesystem.
>
> This looks from reading the diff, but "fragmentation size" is not the
> correct term, see inline.
>
> -Otto
>
> >
> > Index: sbin/disklabel/disklabel.c
> > ===================================================================
> > RCS file: /cvs/src/sbin/disklabel/disklabel.c,v
> > retrieving revision 1.227
> > diff -u -p -u -p -r1.227 disklabel.c
> > --- sbin/disklabel/disklabel.c 25 Feb 2018 17:24:44 -0000 1.227
> > +++ sbin/disklabel/disklabel.c 27 Mar 2018 10:42:59 -0000
> > @@ -1100,9 +1100,24 @@ gottype:
> >
> > case FS_BSDFFS:
> > NXTNUM(fsize, fsize, &errstr);
> > - if (fsize == 0)
> > + if (fsize < lp->d_secsize ||
> > + (fsize % lp->d_secsize) != 0) {
> > + warnx("line %d: "
> > + "bad fragmentation size: %s",
>
> Should be "fragment size"
>
> > + lineno, cp);
> > + errors++;
> > break;
> > + }
> > NXTNUM(v, v, &errstr);
> > + if (v < fsize || (fsize != v &&
> > + fsize * 2 != v && fsize * 4 != v &&
> > + fsize * 8 != v)) {
> > + warnx("line %d: "
> > + "bad block size: %s",
> > + lineno, cp);
> > + errors++;
> > + break;
> > + }
> > pp->p_fragblock =
> > DISKLABELV1_FFS_FRAGBLOCK(fsize, v / fsize);
> > NXTNUM(pp->p_cpg, pp->p_cpg, &errstr);
> > Index: sbin/disklabel/editor.c
> > ===================================================================
> > RCS file: /cvs/src/sbin/disklabel/editor.c,v
> > retrieving revision 1.327
> > diff -u -p -u -p -r1.327 editor.c
> > --- sbin/disklabel/editor.c 8 Mar 2018 22:05:17 -0000 1.327
> > +++ sbin/disklabel/editor.c 27 Mar 2018 10:42:59 -0000
> > @@ -2069,16 +2069,16 @@ get_bsize(struct disklabel *lp, int part
> > if (pp->p_fstype != FS_BSDFFS)
> > return (0);
> >
> > + frag = DISKLABELV1_FFS_FRAG(pp->p_fragblock);
> > + fsize = DISKLABELV1_FFS_FSIZE(pp->p_fragblock);
> > +
> > /* Avoid dividing by zero... */
> > - if (pp->p_fragblock == 0)
> > - return(1);
> > + if (frag * fsize < lp->d_secsize)
> > + return (1);
> >
> > if (!expert)
> > goto align;
> >
> > - fsize = DISKLABELV1_FFS_FSIZE(pp->p_fragblock);
> > - frag = DISKLABELV1_FFS_FRAG(pp->p_fragblock);
> > -
> > for (;;) {
> > ui = getuint64(lp, "block size",
> > "Size of ffs blocks. 1, 2, 4 or 8 times ffs fragment size.",
> > @@ -2119,8 +2119,7 @@ align:
> > orig_size = DL_GETPSIZE(pp);
> > orig_offset = DL_GETPOFFSET(pp);
> >
> > - bsize = (DISKLABELV1_FFS_FRAG(pp->p_fragblock) *
> > - DISKLABELV1_FFS_FSIZE(pp->p_fragblock)) / lp->d_secsize;
> > + bsize = (frag * fsize) / lp->d_secsize;
> > if (DL_GETPOFFSET(pp) != starting_sector) {
> > /* Can't change offset of first partition. */
> > adj = bsize - (DL_GETPOFFSET(pp) % bsize);
> > Index: sbin/fsck_ffs/setup.c
> > ===================================================================
> > RCS file: /cvs/src/sbin/fsck_ffs/setup.c,v
> > retrieving revision 1.64
> > diff -u -p -u -p -r1.64 setup.c
> > --- sbin/fsck_ffs/setup.c 5 Jan 2018 09:33:47 -0000 1.64
> > +++ sbin/fsck_ffs/setup.c 27 Mar 2018 10:42:59 -0000
> > @@ -636,6 +636,10 @@ calcsb(char *dev, int devfd, struct fs *
> > fs->fs_frag = DISKLABELV1_FFS_FRAG(pp->p_fragblock);
> > fs->fs_fpg = pp->p_cpg * fs->fs_frag;
> > fs->fs_bsize = fs->fs_fsize * fs->fs_frag;
> > + if (fs->fs_bsize < lp->d_secsize) {
> > + pfatal("%s: INVALID BLOCK FRAGMENTATION SIZE\n", dev);
>
> This should be e.g. "INVALID BLOCK OR FRAGMENT SIZE IN DISKLABEL"
>
>
> > + return (0);
> > + }
> > fs->fs_nspf = DL_SECTOBLK(lp, fs->fs_fsize / lp->d_secsize);
> > for (fs->fs_fsbtodb = 0, i = NSPF(fs); i > 1; i >>= 1)
> > fs->fs_fsbtodb++;
