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From:   Steve Magnani <steve.magnani@digidescorp.com>
To:     jack@suse.com
Cc:     linux-kernel@vger.kernel.org,
        "Steven J . Magnani" <steve@digidescorp.com>
Subject: [PATCH] udf: disallow RW mount without valid integrity descriptor
Date:   Mon, 11 Feb 2019 08:24:38 -0600
Message-Id: <20190211142438.16599-1-steve@digidescorp.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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 <steve@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;