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zfs: reject read(2) of a dirfd with EISDIR

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This is independent of the recently-discussed global change, which is still
in review/discussion stage.

This is effectively a measure for consistency in the ZFS world, where
FreeBSD was the only platform (as far as I could find) that allowed this.
What ZFS exposes is decidedly not useful for any real purposes, to
paraphrase (hopefully faithfully) jhb's findings when exploring this:

The size of a directory in ZFS is the number of directory entries within.
When reading a directory, you would instead get the leading part of its raw
contents; the amount you get being dictated by the "size," i.e. number of
directory entries. There's decidedly (luckily) no stack disclosure happening
here, though the behavior is bizarre and almost certainly a historical
accident.

This change has already been upstreamed to OpenZFS.

MFC after:	1 week
This commit is contained in:
Kyle Evans 2020-05-19 02:41:05 +00:00
parent 3f5fe78b9a
commit 47c7d8327c
1 changed files with 6 additions and 0 deletions
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6
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c
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@ -646,6 +646,12 @@ zfs_read(vnode_t *vp, uio_t *uio, int ioflag, cred_t *cr, caller_context_t *ct)
ZFS_ENTER(zfsvfs);
ZFS_VERIFY_ZP(zp);
/* We don't copy out anything useful for directories. */
if (vp->v_type == VDIR) {
ZFS_EXIT(zfsvfs);
return (SET_ERROR(EISDIR));
}
if (zp->z_pflags & ZFS_AV_QUARANTINED) {
ZFS_EXIT(zfsvfs);
return (SET_ERROR(EACCES));