Re: [PATCH] isofs: fix Rock Ridge CE extent validation on multisession media

[liubaolin]

在 2026/9/7 18:58, Jan Kara 写道:
> On Mon 07-09-26 16:26:02, Baolin Liu wrote:
> > From: Baolin Liu <liubaolin@xxxxxxxxxx>
> >
> > Commit a36d990f5913 ("isofs: validate Rock Ridge CE continuation extent
> > against volume size") compares the CE extent directly with s_nzones.  The
> > extent is an absolute block number, while s_nzones is the number of blocks
> > relative to the selected ISO session.  The comparison is therefore wrong
> > when a multisession disc starts at a non-zero block.
> >
> > isofs_get_last_session() selects the last session on multisession
> > media, and its volume descriptors describe a volume beginning at that
> > session's LBA.
> > For example, a session beginning at LBA 45447 with 64 blocks can contain a
> > valid CE at absolute LBA 45467.  The existing check rejects that CE, so the
> > ER continuation record is not read, Rock Ridge is disabled, and the mount
> > falls back to Joliet names.
> >
> > Save the selected session start in filesystem-block units and validate the
> > CE extent against the half-open interval [session_start, session_end).
> > Scale the session length to the same block units and retain a separate
> > block-device limit.  The lower bound is intentional: accepting arbitrary
> > blocks before the selected session could make a CE read data from a
> > previous session or another filesystem on the device.
> >
> > Only apply the bounds check when cont_extent is non-zero.  A zero extent is
> > the in-memory sentinel indicating that no CE continuation was found, rather
> > than a request to read block zero.
> >
> > For a single-session image, session_start is zero and the effective volume
> > boundary remains unchanged.
> >
> > Build-tested with:
> >
> >      make CONFIG_RUST= CONFIG_RUST_DRIVERS= fs/isofs/
> >
> > Fixes: a36d990f5913 ("isofs: validate Rock Ridge CE continuation extent against volume size")
> > Cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Baolin Liu <liubaolin@xxxxxxxxxx>
>
> Thanks for the fix! I've taken the patch to my tree. I've slighly cleaned
> up the types (use sector_t instead of u64). I've also remove the check
> against sb_bdev_nr_blocks() - if anything, we should have check s_nzones
> fits within the block device earlier, not in Rockridge parsing code.
>
> 								Honza
Hi Honza,
   Thank you for improving and organizing the patch fixes.
Thanks,
Baolin.


> > @@ -101,11 +107,14 @@ static int rock_continue(struct rock_state *rs)
> >   		goto out;
> >   	}
> >   
> > -	if ((unsigned)rs->cont_extent >= ISOFS_SB(rs->inode->i_sb)->s_nzones) {
> > +	if (rs->cont_extent &&
> > +	    (extent < sbi->s_session_start ||
> > +	     extent >= session_end ||
> > +	     extent >= sb_bdev_nr_blocks(sb))) {
> >   		printk(KERN_NOTICE "rock: corrupted directory entry. "
> >   			"extent=%u out of volume (nzones=%lu)\n",
> >   			(unsigned)rs->cont_extent,
> > -			ISOFS_SB(rs->inode->i_sb)->s_nzones);
> > +			sbi->s_nzones);
> >   		ret = -EIO;
> >   		goto out;
> >   	}
> > --
> > 2.51.0