[PATCH] udf: disallow RW mount without valid integrity descriptor

[Steve Magnani]

Refuse to mount a volume read-write without a coherent Logical Volume
Integrity Descriptor, because we can't generate truly unique IDs without 
one.

This fixes a bug where all inodes created on a UDF filesystem following
mount without a coherent LVID are assigned UID 0.

Signed-off-by: Steven J. Magnani <st...@digidescorp.com>
---
--- a/fs/udf/super.c    2018-11-16 06:43:00.622344354 -0600
+++ b/fs/udf/super.c    2019-02-11 08:08:00.478331631 -0600
@@ -1474,6 +1474,17 @@ static int udf_load_logicalvol(struct su
        if (lvd->integritySeqExt.extLength)
                udf_load_logicalvolint(sb, leea_to_cpu(lvd->integritySeqExt));
        ret = 0;
+
+       if (!sbi->s_lvid_bh) {
+               /* We can't generate UIDs without a valid LVID */
+               if (sb_rdonly(sb))
+                       UDF_SET_FLAG(sb, UDF_FLAG_RW_INCOMPAT);
+               else {
+                       udf_warn(sb, "Damaged or missing LVID, forcing "
+                                    "readonly mount\n");
+                       ret = -EACCES;
+               }
+       }
 out_bh:
        brelse(bh);
        return ret;