On Thursday 15 February 2018 09:43:12 Jan Kara wrote:
> On Wed 14-02-18 18:26:03, Pali Rohár wrote:
> > On Wednesday 14 February 2018 11:28:46 Jan Kara wrote:
> > > According to ECMA-167 3/8.4.2 Volume Descriptor Pointer is terminating
> > > current extent of Volume Descriptor Sequence. Also according to ECMA-167
> > > 3/8.4.3 Volume Descriptor Sequence Number is not significant for Volume
> > > Descriptor Pointers. Simplify the handling of Volume Descriptor Pointers
> > > to take this into account.
> > >
> > > Signed-off-by: Jan Kara <jack@xxxxxxx>
> > > ---
> > > fs/udf/super.c | 41 ++++++++++++++++-------------------------
> > > 1 file changed, 16 insertions(+), 25 deletions(-)
> > >
> > > diff --git a/fs/udf/super.c b/fs/udf/super.c
> > > index 5c5d5fd513cc..f80b97173acd 100644
> > > --- a/fs/udf/super.c
> > > +++ b/fs/udf/super.c
> > > @@ -1615,7 +1615,6 @@ static noinline int udf_process_sequence(
> > > bool done = false;
> > > uint32_t vdsn;
> > > uint16_t ident;
> > > - long next_s = 0, next_e = 0;
> > > int ret;
> > > unsigned int indirections = 0;
> > >
> > > @@ -1647,19 +1646,22 @@ static noinline int udf_process_sequence(
> > > }
> > > break;
> > > case TAG_IDENT_VDP: /* ISO 13346 3/10.3 */
> > > - curr = &vds[VDS_POS_VOL_DESC_PTR];
> > > - if (vdsn >= curr->volDescSeqNum) {
> > > - curr->volDescSeqNum = vdsn;
> > > - curr->block = block;
> > > -
> > > - vdp = (struct volDescPtr *)bh->b_data;
> > > - next_s = le32_to_cpu(
> > > - vdp->nextVolDescSeqExt.extLocation);
> > > - next_e = le32_to_cpu(
> > > - vdp->nextVolDescSeqExt.extLength);
> > > - next_e = next_e >> sb->s_blocksize_bits;
> > > - next_e += next_s - 1;
> > > + if (++indirections > UDF_MAX_TD_NESTING) {
> > > + udf_err(sb, "too many Volume Descriptor "
> > > + "Pointers (max %u supported)\n",
> > > + UDF_MAX_TD_NESTING);
> > > + brelse(bh);
> > > + return -EIO;
> > > }
> > > +
> > > + vdp = (struct volDescPtr *)bh->b_data;
> > > + block = le32_to_cpu(vdp->nextVolDescSeqExt.extLocation);
> >
> > Another pathological case: disc with two (or more) VDP descriptors and
> > each points to another in cycle.
> >
> > Seems that this would not cause infinite loop due to
> > UDF_MAX_TD_NESTING, but probably can cause some troubles.
>
> Yes. Such disk is invalid so our only goal is not to crash / livelock the
> kernel and UDF_MAX_TD_NESTING protection is enough for that.
Ok, then you can add my Acked-by on whole patch series.
Acked-by: Pali Rohár <pali.rohar@xxxxxxxxx>
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